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Friday, December 1, 2023

Federation

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Federation
  Federal states
The pathway of regional integration or separation

A federation (also known as a federal state) is a political entity characterized by a union of partially self-governing provinces, states, or other regions under a central federal government (federalism). In a federation, the self-governing status of the component states, as well as the division of power between them and the central government, is constitutionally entrenched and may not be altered by a unilateral decision, neither by the component states nor the federal political body. Alternatively, a federation is a form of government in which sovereign power is formally divided between a central authority and a number of constituent regions so that each region retains some degree of control over its internal affairs.

It is often argued that federal states where the central government has overriding powers are not truly federal states. For example, such overriding powers may include: the constitutional authority to suspend a constituent state's government by invoking gross mismanagement or civil unrest, or to adopt national legislation that overrides or infringes on the constituent states' powers by invoking the central government's constitutional authority to ensure "peace and good government" or to implement obligations contracted under an international treaty.

The governmental or constitutional structure found in a federation is considered to be federalist, or to be an example of federalism. It can be considered the opposite of another system, the unitary state. France and Japan, for example, have been unitary for many centuries. The Austrian Empire was a unitary state with crown lands, after the transformation into the Austria-Hungary monarchy the remaining crown lands of so-called Cisleithania became federated as Länder of the Republic of Austria through the implementation of its constitution. Germany, with its 16 states, or Länder, and Nigeria, with its 36 states and federal capital territory, are examples of federations. Federations are often multi-ethnic and cover a large area of territory (such as Russia, the United States, Canada, India, Brazil or Australia), but neither is necessarily the case (such as Saint Kitts and Nevis or the Federated States of Micronesia).

History

Several ancient chiefdoms and kingdoms, such as the 4th-century BCE League of Corinth, Noricum in Central Europe, and the Iroquois Confederacy in pre-Columbian North America, could be described as federations or confederations. The Old Swiss Confederacy was an early example of formal non-unitary statehood.

Several colonies and dominions in the New World consisted of autonomous provinces, transformed into federal states upon independence such as the United States, and various countries in Latin America (see Spanish American wars of independence). Some of the New World federations failed; the Federal Republic of Central America broke up into independent states less than 20 years after its founding. Others, such as Argentina, have shifted between federal, confederal, and unitary systems, before settling into federalism. Brazil became a federation only after the fall of the monarchy, and Venezuela became a federation after the Federal War. Australia and Canada are also federations.

Germany is another nation-state that has switched between confederal, federal and unitary rules, since the German Confederation was founded in 1815. The North German Confederation, the succeeding German Empire and the Weimar Republic were federations.

Founded in 1922, the Soviet Union was formally a federation of Soviet republics, autonomous republics and other federal subjects, though in practice highly centralized under the government of the Soviet Union. The Russian Federation has inherited a similar system.

India, Pakistan, Nigeria and Malaysia (then Federation of Malaya) became federations on or shortly before becoming independent from the British Empire.

In some recent cases, federations have been instituted as a measure to handle ethnic conflict within a state, such as Bosnia and Herzegovina, and Iraq since 2005 as well as Somalia since 2012

With the United States Constitution having become effective on 4 March 1789, the United States is the oldest surviving federation, while the newest federation is Nepal, after its constitution went into effect on 20 September 2015.

Currently, or as of 2023, there are 27 federations or federal countries.

Federations and other forms of state

A map of the Russian Federation, showing its eighty-three federal subjects before the annexation of Crimea in 2014
A map of Brazil, showing its twenty-six constituent states and the Federal District
A map of the Federal Democratic Republic of Ethiopia, showing its regions
A map of the Federal Republic of Nigeria, showing its 36 states and the Federal Capital Territory
A map of the United Mexican States (Mexico), showing its thirty-one constituent states and Mexico City
A map of the United States of America showing its fifty constituent states and the District of Columbia
A map of Canada showing its ten provinces and three territories
A map of Australia showing its six states and ten territories
A map of the Federal Republic of Germany showing its sixteen constituent states (Länder) including three city-states

Federations

The component states are in some sense sovereign, insofar as certain powers are reserved to them that may not be exercised by the central government. However, a federation is more than a mere loose alliance of independent states. The component states of a federation usually possess no powers in relation to foreign policy and so enjoy no independent status under international law. However, German Länder have that power, which is beginning to be exercised on a European level.

Some federations are called asymmetric because some states have more autonomy than others. An example of such a federation is Malaysia, in which Sarawak and Sabah agreed to form the federation on different terms and conditions from the states of Peninsular Malaysia.

A federation often emerges from an initial agreement between several separate states. The purpose can be the will to solve mutual problems and to provide for mutual defense or to create a nation-state for an ethnicity spread over several states. The former was the case with the United States and Switzerland. However, as the histories of countries and nations vary, the federalist system of a state can be quite different from these models. Australia, for instance, is unique in that it came into existence as a nation by the democratic vote of the citizens of each state, who voted "yes" in referendums to adopt the Australian Constitution. Brazil, on the other hand, has experienced both the federal and the unitary state during its history. Some present-day states of the Brazilian federation retain borders set during the Portuguese colonization (before the very existence of the Brazilian state), whereas the latest state, Tocantins, was created by the 1988 Constitution for chiefly administrative reasons.

Seven of the top eight largest countries by area are governed as federations.

Unitary states

A unitary state is sometimes one with only a single, centralized, national tier of government. However, unitary states often also include one or more self-governing regions. The difference between a federation and this kind of unitary state is that in a unitary state the autonomous status of self-governing regions exists by the sufferance of the central government, and may be unilaterally revoked. While it is common for a federation to be brought into being by agreement between a number of formally independent states, in a unitary state self-governing regions are often created through a process of devolution, where a formerly centralized state agrees to grant autonomy to a region that was previously entirely subordinate. Thus, federations are often established voluntarily from "below" whereas devolution grants self-government from "above".

Confederation

The Swiss Confederation and its 26 cantons

A confederation, in modern political terms, is usually limited to a permanent union of sovereign states for common action in relation to other states.[2] The closest entity in the world to a confederation at this time is the European Union. While the word confederation was officially used when the Canadian federal system was established in 1867, the term refers only to the process and not the resulting state since Canadian provinces are not sovereign and do not claim to be. In the case of Switzerland, while the country is still known officially as the Swiss Confederation, this is now a misnomer since the Swiss cantons lost their sovereign status in 1848.

In Belgium, however, the opposite movement is underway. Belgium was founded as a centralized state, after the French model, but has gradually been reformed into a federal state by consecutive constitutional reforms since the 1970s. Moreover, although nominally called a federal state, the country's structure already has a number of confederational traits. At present, there is a growing movement to transform the existing federal state into a looser confederation with two or three constitutive states and/or two special regions.

A confederation is most likely to feature three differences when contrasted with a federation: (1) No real direct powers: many confederal decisions are externalized by member-state legislation; (2) Decisions on day-to-day-matters are not taken by simple majority but by special majorities or even by consensus or unanimity (veto for every member); (3) Changes of the constitution, usually a treaty, require unanimity.

Over time these terms acquired distinct connotations leading to the present difference in definition. An example of this is the United States under the Articles of Confederation. The Articles established a national government under what today would be defined as a federal system (albeit with a comparatively weaker federal government). However, Canadians, designed with a stronger central government than the U.S. in the wake of the Civil War of the latter, use the term "Confederation" to refer to the formation or joining, not the structure, of Canada. Legal reforms, court rulings, and political compromises have decentralized Canada in practice since its formation in 1867.

Empire

An empire is a multi-ethnic state, multinational state, or a group of nations with a central government established usually through coercion (on the model of the Roman Empire). An empire often includes self-governing regions, but these will possess autonomy only at the sufferance of the central government. On the other hand, a political entity that is an empire in name, may comprise several partly autonomous kingdoms organised together in a federation, with the empire being ruled over by an emperor or senior king (great king, high king, king of kings...). One example of this was the German Empire (1871–1918).

Comparison with other systems of autonomy

Federacy

A federacy is a unitary state that incorporates one or more self-governing autonomous areas. It is distinguished from a federation in that the constitutional structure of the state is still unitary, but incorporates federalist principles. Some federacies, notably Åland, were established through international treaty.

Devolution

A federation differs from a devolved state, such as Indonesia and the United Kingdom, because, in a devolved state, the central government can revoke the independence of the subunits (Scottish Parliament, the Senedd and the Northern Ireland Assembly in the case of the United Kingdom) without changing the constitution. In some cases, such as the autonomous communities of Spain, devolution has led to federation in all but name, or "federation without federalism".

Crown dependencies

The relation between the Crown Dependencies of the Isle of Man and the bailiwicks of Guernsey and Jersey in the Channel Islands and the United Kingdom is very similar to a federate relation: the Islands enjoy independence from the United Kingdom, which, via The Crown, takes care of their foreign relations and defense – although the UK Parliament does have overall power to legislate for the dependencies. However, the islands are neither an incorporated part of the United Kingdom nor are they considered to be independent or associated states. The islands do not have a monarch, per se; rather in the Isle of Man the British Monarch is, ex officio, Lord of Mann, and in the Bailiwicks of Guernsey and Jersey, the British Monarch rules as the Duke of Normandy.

Dependent territories

Dependent territories, such as the British overseas territories, are vested with varying degrees of power; some enjoy considerable independence from the sovereign state, which only takes care of their foreign relations and defense. However, they are neither considered to be part of it nor recognized as sovereign or associated states.

De facto federations

The distinction between a federation and a unitary state is often quite ambiguous. A unitary state may closely resemble a federation in structure and, while a central government may possess the theoretical right to revoke the autonomy of a self-governing region, it may be politically difficult for it to do so in practice. The self-governing regions of some unitary states also often enjoy greater autonomy than those of some federations. For these reasons, it is sometimes argued that some modern unitary states are de facto federations.

De facto federations, or quasi-federations, are often termed "regional states".

Spain

The Autonomous communities of Spain

Spain is suggested as one possible de facto federation as it grants more self-government to its autonomous communities than are retained by the constituent entities of most federations. For the Spanish parliament to revoke the autonomy of regions such as Galicia, Catalonia or the Basque Country would be a political near-impossibility, though nothing bars it legally. The Spanish parliament has, however, suspended the autonomy of Catalonia in response to the Catalan declaration of independence, in the lead-up to the 2017 Catalan election. Additionally, some autonomies such as Navarre or the Basque Country have full control over taxation and spending, transferring a payment to the central government for the common services (military, foreign relations, macroeconomic policy). For example, scholar Enrique Guillén López discusses the "federal nature of Spain's government (a trend that almost no one denies)." Each autonomous community is governed by a Statute of Autonomy (Estatuto de Autonomía) under the Spanish Constitution of 1978.

South Africa

Provinces of South Africa

Although South Africa bears some elements of a federal system, such as the allocation of certain powers to provinces, it is nevertheless constitutionally and functionally a unitary state.

European Union

The European Union (EU) is a sui generis political union or confederation (the assemblage of societies or an association of two or more states into one state). Robert Schuman, the initiator of the European Community system, wrote that a transnational Community like the founding of the European Coal and Steel Community lay midway between an association of States where they retained complete independence and a federation leading to a fusion of States in a super-state. The Founding Fathers of the European Union wrote the Europe Declaration (Charter of the Community) at the time of the signing of the Treaty of Paris on 18 April 1951 saying that Europe should be organized on a transnational foundation. They envisaged a structure quite different from a federation called the European Political Community.

The EU is a three-pillar structure of the original supranational European Economic Community and the nuclear energy cooperation and non-proliferation treaty, Euratom, plus two largely intergovernmental pillars dealing with External Affairs and Justice and Home Affairs. The EU is therefore not a de jure federation, although some academic observers conclude that after 50 years of institutional evolution since the Treaties of Rome it is becoming one. The European Union possesses attributes of a federal state. However, its central government is far weaker than that of most federations and the individual members are sovereign states under international law, so it is usually characterized as an unprecedented form of supra-national union. The EU has responsibility for important areas such as trade, monetary union, agriculture, and fisheries. Nonetheless, EU member states retain the right to act independently in matters of foreign policy and defense, and also enjoy a near-monopoly over other major policy areas such as criminal justice and taxation. Since the Treaty of Lisbon, the Member States' right to leave the Union is codified, and the Union operates with more qualified majority voting (rather than unanimity) in many areas.

By the signature of this Treaty, the participating Parties give proof of their determination to create the first supranational institution and that thus they are laying the true foundation of an organized Europe. This Europe remains open to all nations. We profoundly hope that other nations will join us in our common endeavor.

— Europe Declaration, signed by Konrad Adenauer (West Germany), Paul van Zeeland, Joseph Meurice (Belgium) Robert Schuman (France) Count Sforza (Italy) Joseph Bech (Luxembourg) and Dirk Stikker, J. R. M. van den Brink (The Netherlands).

Europe has charted its own brand of constitutional federalism.

— European Constitutionalism Beyond the State. Edited with Marlene Wind (Cambridge Univ. Press, 2003) page 23, Joseph H. H. Weiler

Those uncomfortable using the "F" word in the EU context should feel free to refer to it as a quasi-federal or federal-like system. Nevertheless, for the purposes of the analysis here, the EU has the necessary attributes of a federal system. It is striking that while many scholars of the EU continue to resist analyzing it as a federation, most contemporary students of federalism view the EU as a federal system. (See, for instance, Bednar, Filippov et al., McKay, Kelemen, Defigueido and Weingast)

A more nuanced view has been given by the German Constitutional Court. Here the EU is defined as 'an association of sovereign national states (Staatenverbund)'. With this view, the European Union resembles more of a confederation.

People's Republic of China

Constitutionally, the power vested in the special administrative regions of the People's Republic is granted from the Central People's Government, through a decision by the National People's Congress. However, there have been certain largely informal grants of power to the provinces, to handle economic affairs and implement national policies, resulting in a system some have termed federalism "with Chinese characteristics".

Myanmar

Constitutionally a unitary state, the political system in Myanmar bears many elements of federalism. Each administrative division has its own cabinets and chief ministers, making it more like a federation rather than a unitary state.

Wallis and Futuna

The French overseas collectivity Wallis and Futuna maintains some quasi-federation attributes. The territory is divided into three traditional chiefdoms: Uvea, Sigave, and Alo. The chiefdoms are allowed to have their own legal system which have to be implemented along with French legal system.

Internal controversy and conflict

The United Provinces of Central America was a short-lived federal republic.

Certain forms of political and constitutional dispute are common to federations. One issue is that the exact division of power and responsibility between federal and regional governments is often a source of controversy. Often, as is the case with the United States, such conflicts are resolved through the judicial system, which delimits the powers of federal and local governments. The relationship between federal and local courts varies from nation to nation and can be a controversial and complex issue in itself.

Another common issue in federal systems is the conflict between regional and national interests, or between the interests and aspirations of different ethnic groups. In some federations the entire jurisdiction is relatively homogeneous and each constituent state resembles a miniature version of the whole; this is known as 'congruent federalism'. On the other hand, incongruent federalism exists where different states or regions possess distinct ethnic groups.

The ability of a federal government to create national institutions that can mediate differences that arise because of linguistic, ethnic, religious, or other regional differences is an important challenge. The inability to meet this challenge may lead to the secession of parts of a federation or to civil war, as occurred in the United States (southern states sought to protect the institution of slavery while northern states opposed it, with a catalysis occurring in the then–Kansas Territory), in Nigeria and in Switzerland. In the case of Malaysia, Singapore was expelled from the federation because of rising racial tension. In some cases, internal conflict may lead a federation to collapse entirely, as occurred the Federation of Rhodesia and Nyasaland, the Gran Colombia, the United Provinces of Central America, and the West Indies Federation.

Federal governments

The federal government is the common government of a national or supranational federation. A federal government may have distinct powers at various levels authorized or delegated to it by its member states. The structure of federal governments vary. Based on a broad definition of a basic federalism, there are two or more levels of government that exist within an established territory and govern through common institutions with overlapping or shared powers as prescribed by a constitution.

The federal government is the government at the level of the sovereign state. Usual responsibilities of this level of government are maintaining national security and exercising international diplomacy, including the right to sign binding treaties. Basically, a modern federal government, within the limits defined by its constitution, has the power to make laws for the whole country, unlike local governments. As originally written, the United States Constitution was created to limit the federal government from exerting power over the states by enumerating only specific powers. It was further limited by the addition of the Tenth Amendment contained in the Bill of Rights and the Eleventh Amendment. However, later amendments, particularly the Fourteenth Amendment, gave the federal government considerable authority over states.

Federal government within this structure are the government ministries and departments and agencies to which the ministers of government are assigned.

Contemporary

There are 27 federations in the world, with 6 each in Africa, Asia and Europe, 4 in North America, 3 in South America and 2 in Oceania.

Current federations
Year est. Federation Type

Structure Top-level subdivisions (federated and other) Major federated units Minor units (federated or other)
1853  Argentine Republic R Presidential Provinces of Argentina 23 provinces 1 autonomous city
1901  Commonwealth of Australia M Parliamentary States and territories of Australia 6 states 3 internal territories (of which 2 are self-governing) and 7 external territories
1920  Republic of Austria R Parliamentary States of Austria 9 states (Länder or Bundesländer) incl. the city-state of Vienna
1993  Kingdom of Belgium M Parliamentary Divisions of Belgium 3 communities, 3 regions 3 communitarian commissions
1995  Bosnia and Herzegovina R Parliamentary Divisions of Bosnia and Herzegovina 2 entities, one of which is itself a federation of 10 cantons 1 district
1889  Federative Republic of Brazil R Presidential Federative units of Brazil 27 federative units (of which one is a federal district and the others are states)
1867  Canada M Parliamentary Provinces and territories of Canada 10 provinces 3 territories
1975  Union of the Comoros R Presidential Autonomous Islands of the Comoros 3 islands
1995  Federal Democratic Republic of Ethiopia R Parliamentary Regions and chartered cities of Ethiopia 11 regions 2 chartered cities
1949  Federal Republic of Germany R Parliamentary States of Germany 16 states (Länder or Bundesländer) incl. the city-states of Berlin, Hamburg, and Bremen
1947  Republic of India R Parliamentary States and union territories of India 28 states 8 union territories, including a 1 national capital territory
2005  Republic of Iraq R Parliamentary Governorates of Iraq 19 provinces (governorates)
1963  Malaysia M Parliamentary States of Malaysia 13 states 3 federal territories
1824  United Mexican States R Presidential States of Mexico 32 federal entities, which are 31 states and its capital Mexico City
1979  Federated States of Micronesia R Presidential Administrative divisions of Micronesia 4 states
2015    Federal Democratic Republic of Nepal R Parliamentary Provinces of Nepal 7 provinces
1960  Federal Republic of Nigeria R Presidential Subdivisions of Nigeria 36 states 1 federal capital territory
1947  Islamic Republic of Pakistan R Parliamentary Provinces and territories of Pakistan 4 provinces 2 autonomous territories and 1 federal capital territory
1992  Russian Federation R Semi-presidential Federal subjects of Russia 46 oblasts, 22 republics, 9 krais, 4 autonomous okrugs, 3 federal-level cities, 1 autonomous oblast
1983  Federation of Saint Christopher and Nevis M Parliamentary The islands St. Kitts and Nevis 1 federal unit (the island of Nevis) The island of Saint Kitts (directly administered by the federal government)
2012  Federal Republic of Somalia R Parliamentary Federal Member States of Somalia 5 States
2011  Republic of South Sudan R Presidential States of South Sudan 10 states 3 administrative areas (which one of them has special administrative status)
1956  Republic of the Sudan R Military junta States of Sudan 18 states
1848   Swiss Confederation R Directorial Cantons of Switzerland 26 cantons
1971  United Arab Emirates M Semi-constitutional monarchy Emirates of the UAE 7 emirates
1776  United States of America R Presidential U.S. States and territories 50 states 1 federal district; 16 territories
1863  Bolivarian Republic of Venezuela R Presidential States of Venezuela 23 states 1 federal district, 1 federal dependency
  • R = Federal republic; M = Federal monarchy (in the loose sense).

  • That is, first-level subdivisions possessing less autonomy than the major federated units.

  • Brčko District is de jure part of both entities, and de facto administered separately from either.

  • 20 provinces during the Empire of Brazil 1822–89

  • As an independent Dominion; republic declared in 1950

  • As the Federation of Nigeria; republic declared in 1963

  • As an independent Dominion; republic declared in 1956

  • After the dissolution of the Soviet Union, a new Treaty of Federation was signed in 1992, which did not include all of the same components as the Soviet Union.

  • Three pairs of cantons have less power at federal level than the other 20 cantons, but the same degree of internal autonomy.

  • The United States Constitution, which replaced the Articles of Confederation and Perpetual Union, was drafted in 1787 and was ratified in 1788. The first Congress and President did not take office until March 1789.

    1. Of the 5 territories that are permanently inhabited, all are unincorporated, two are commonwealths and a third is formally unorganized. Of the other 11, one is incorporated and all are unorganized; together they form the United States Minor Outlying Islands. The term insular area includes both territories and places with a Compact of Free Association.

    Defunct

    Some of the proclaimed Arab federations were confederations de facto.

    Thiol

    From Wikipedia, the free encyclopedia
    https://en.wikipedia.org/wiki/Thiol
    Thiol with a   blue highlighted sulfhydryl group.

    In organic chemistry, a thiol (/ˈθɒl/; from Ancient Greek θεῖον (theion) 'sulfur'), or thiol derivative, is any organosulfur compound of the form R−SH, where R represents an alkyl or other organic substituent. The −SH functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols (that is, sulfur takes the place of oxygen in the hydroxyl (−OH) group of an alcohol), and the word is a blend of "thio-" with "alcohol".

    Many thiols have strong odors resembling that of garlic or rotten eggs. Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless), and the "smell of natural gas" is due to the smell of the thiol used as the odorant. Thiols are sometimes referred to as mercaptans (/mərˈkæptæn/) or mercapto compounds, a term introduced in 1832 by William Christopher Zeise and is derived from the Latin mercurio captāns ('capturing mercury') because the thiolate group (RS), also termed as Mercaptide, bonds very strongly with mercury compounds.

    Structure and bonding

    Thiols having the structure R−SH, in which an alkyl group (R) is attached to a sulfhydryl group (SH), are referred to as alkanethiols or alkyl thiols. Thiols and alcohols have similar connectivity. Because sulfur atoms are larger than oxygen atoms, C−S bond lengths – typically around 180 picometres – are about 40 picometers longer than typical C−O bonds. The C−S−H angles approach 90° whereas the angle for the C−O−H group is more obtuse. In solids and liquids, the hydrogen-bonding between individual thiol groups is weak, the main cohesive force being Van der Waals interactions between the highly polarizable divalent sulfur centers.

    The S−H bond is much weaker than the O−H bond as reflected in their respective bond dissociation energies (BDE). For CH3S−H, the BDE is 366 kJ/mol (87 kcal/mol), while for CH3O−H, the BDE is 440 kJ/mol (110 kcal/mol).

    An S−H bond is moderately polar because of the small difference in the electronegativity of sulfur and hydrogen. In contrast, O−H bonds in hydroxyl groups are more polar. Thiols have a lower dipole moment relative to their corresponding alcohols.

    Nomenclature

    There are several ways to name the alkylthiols:

    • The suffix -thiol is added to the name of the alkane. This method is nearly identical to naming an alcohol and is used by the IUPAC, e.g. CH3SH would be methanethiol.
    • The word mercaptan replaces alcohol in the name of the equivalent alcohol compound. Example: CH3SH would be methyl mercaptan, just as CH3OH is called methyl alcohol.
    • The term sulfhydryl- or mercapto- is used as a prefix, e.g. mercaptopurine.

    Physical properties

    Odor

    Many thiols have strong odors resembling that of garlic. The odors of thiols, particularly those of low molecular weight, are often strong and repulsive. The spray of skunks consists mainly of low-molecular-weight thiols and derivatives. These compounds are detectable by the human nose at concentrations of only 10 parts per billion. Human sweat contains (R)/(S)-3-methyl-3-mercapto-1-ol (MSH), detectable at 2 parts per billion and having a fruity, onion-like odor. (Methylthio)methanethiol (MeSCH2SH; MTMT) is a strong-smelling volatile thiol, also detectable at parts per billion levels, found in male mouse urine. Lawrence C. Katz and co-workers showed that MTMT functioned as a semiochemical, activating certain mouse olfactory sensory neurons, attracting female mice. Copper has been shown to be required by a specific mouse olfactory receptor, MOR244-3, which is highly responsive to MTMT as well as to various other thiols and related compounds. A human olfactory receptor, OR2T11, has been identified which, in the presence of copper, is highly responsive to the gas odorants (see below) ethanethiol and t-butyl mercaptan as well as other low molecular weight thiols, including allyl mercaptan found in human garlic breath, and the strong-smelling cyclic sulfide thietane.

    Thiols are also responsible for a class of wine faults caused by an unintended reaction between sulfur and yeast and the "skunky" odor of beer that has been exposed to ultraviolet light.

    Not all thiols have unpleasant odors. For example, furan-2-ylmethanethiol contributes to the aroma of roasted coffee, whereas grapefruit mercaptan, a monoterpenoid thiol, is responsible for the characteristic scent of grapefruit. The effect of the latter compound is present only at low concentrations. The pure mercaptan has an unpleasant odor.

    In the United States, natural gas distributors were required to add thiols, originally ethanethiol, to natural gas (which is naturally odorless) after the deadly New London School explosion in New London, Texas, in 1937. Many gas distributors were odorizing gas prior to this event. Most currently-used gas odorants contain mixtures of mercaptans and sulfides, with t-butyl mercaptan as the main odor constituent in natural gas and ethanethiol in liquefied petroleum gas (LPG, propane). In situations where thiols are used in commercial industry, such as liquid petroleum gas tankers and bulk handling systems, an oxidizing catalyst is used to destroy the odor. A copper-based oxidation catalyst neutralizes the volatile thiols and transforms them into inert products.

    Boiling points and solubility

    Thiols show little association by hydrogen bonding, both with water molecules and among themselves. Hence, they have lower boiling points and are less soluble in water and other polar solvents than alcohols of similar molecular weight. For this reason also, thiols and their corresponding sulfide functional group isomers have similar solubility characteristics and boiling points, whereas the same is not true of alcohols and their corresponding isomeric ethers.

    Bonding

    The S−H bond in thiols is weak compared to the O−H bond in alcohols. For CH3X−H, the bond enthalpies are 365.07±2.1 kcal/mol for X = S and 440.2±3.0 kcal/mol for X = O. Hydrogen-atom abstraction from a thiol gives a thiyl radical with the formula RS, where R = alkyl or aryl.

    Characterization

    Volatile thiols are easily and almost unerringly detected by their distinctive odor. Sulfur-specific analyzers for gas chromatographs are useful. Spectroscopic indicators are the D2O-exchangeable SH signal in the 1H NMR spectrum (33S is NMR-active but signals for divalent sulfur are very broad and of little utility). The νSH band appears near 2400 cm−1 in the IR spectrum. In the nitroprusside reaction, free thiol groups react with sodium nitroprusside and ammonium hydroxide to give a red colour.

    Preparation

    In industry, methanethiol is prepared by the reaction of hydrogen sulfide with methanol. This method is employed for the industrial synthesis of methanethiol:

    CH3OH + H2S → CH3SH + H2O

    Such reactions are conducted in the presence of acidic catalysts. The other principal route to thiols involves the addition of hydrogen sulfide to alkenes. Such reactions are usually conducted in the presence of an acid catalyst or UV light. Halide displacement, using the suitable organic halide and sodium hydrogen sulfide has also been used.

    Another method entails the alkylation of sodium hydrosulfide.

    RX + NaSH → RSH + NaX (X = Cl, Br, I)

    This method is used for the production of thioglycolic acid from chloroacetic acid.

    Laboratory methods

    In general, on the typical laboratory scale, the direct reaction of a haloalkane with sodium hydrosulfide is inefficient owing to the competing formation of sulfides. Instead, alkyl halides are converted to thiols via an S-alkylation of thiourea. This multistep, one-pot process proceeds via the intermediacy of the isothiouronium salt, which is hydrolyzed in a separate step:

    CH3CH2Br + SC(NH2)2 → [CH3CH2SC(NH2)2]Br
    [CH3CH2SC(NH2)2]Br + NaOH → CH3CH2SH + OC(NH2)2 + NaBr

    The thiourea route works well with primary halides, especially activated ones. Secondary and tertiary thiols are less easily prepared. Secondary thiols can be prepared from the ketone via the corresponding dithioketals. A related two-step process involves alkylation of thiosulfate to give the thiosulfonate ("Bunte salt"), followed by hydrolysis. The method is illustrated by one synthesis of thioglycolic acid:

    ClCH2CO2H + Na2S2O3 → Na[O3S2CH2CO2H] + NaCl
    Na[O3S2CH2CO2H] + H2O → HSCH2CO2H + NaHSO4

    Organolithium compounds and Grignard reagents react with sulfur to give the thiolates, which are readily hydrolyzed:

    RLi + S → RSLi
    RSLi + HCl → RSH + LiCl

    Phenols can be converted to the thiophenols via rearrangement of their O-aryl dialkylthiocarbamates.

    Thiols are prepared by reductive dealkylation of sulfides, especially benzyl derivatives and thioacetals.

    Thiophenols are produced by S-arylation or the replacement of diazonium leaving group with sulfhydryl anion (SH):

    ArN+
    2
    + SH → ArSH + N2

    Reactions

    Akin to the chemistry of alcohols, thiols form sulfides, thioacetals, and thioesters, which are analogous to ethers, acetals, and esters respectively. Thiols and alcohols are also very different in their reactivity, thiols being more easily oxidized than alcohols. Thiolates are more potent nucleophiles than the corresponding alkoxides.

    S-Alkylation

    Thiols, or more specific their conjugate bases, are readily alkylated to give sulfides:

    RSH + R′Br + B → RSR′ + [HB]Br  (B = base)

    Acidity

    Thiols are easily deprotonated. Relative to the alcohols, thiols are more acidic. The conjugate base of a thiol is called a thiolate. Butanethiol has a pKa of 10.5 vs 15 for butanol. Thiophenol has a pKa of 6, versus 10 for phenol. A highly acidic thiol is pentafluorothiophenol (C6F5SH) with a pKa of 2.68. Thus, thiolates can be obtained from thiols by treatment with alkali metal hydroxides.

    Synthesis of thiophenolate from thiophenol

    Redox

    Thiols, especially in the presence of base, are readily oxidized by reagents such as bromine and iodine to give an organic disulfide (R−S−S−R).

    2 R−SH + Br2 → R−S−S−R + 2 HBr

    Oxidation by more powerful reagents such as sodium hypochlorite or hydrogen peroxide can also yield sulfonic acids (RSO3H).

    R−SH + 3 H2O2 → RSO3H + 3 H2O

    Oxidation can also be effected by oxygen in the presence of catalysts:

    2 R–SH + 12 O2 → RS−SR + H2O

    Thiols participate in thiol-disulfide exchange:

    RS−SR + 2 R′SH → 2 RSH + R′S−SR′

    This reaction is important in nature.

    Metal ion complexation

    With metal ions, thiolates behave as ligands to form transition metal thiolate complexes. The term mercaptan is derived from the Latin mercurium captans (capturing mercury) because the thiolate group bonds so strongly with mercury compounds. According to hard/soft acid/base (HSAB) theory, sulfur is a relatively soft (polarizable) atom. This explains the tendency of thiols to bind to soft elements and ions such as mercury, lead, or cadmium. The stability of metal thiolates parallels that of the corresponding sulfide minerals.

    Thioxanthates

    Thiolates react with carbon disulfide to give thioxanthate (RSCS
    2
    ).

    Thiyl radicals

    Free radicals derived from mercaptans, called thiyl radicals, are commonly invoked to explain reactions in organic chemistry and biochemistry. They have the formula RS where R is an organic substituent such as alkyl or aryl. They arise from or can be generated by a number of routes, but the principal method is H-atom abstraction from thiols. Another method involves homolysis of organic disulfides. In biology thiyl radicals are responsible for the formation of the deoxyribonucleic acids, building blocks for DNA. This conversion is catalysed by ribonucleotide reductase (see figure). Thiyl intermediates also are produced by the oxidation of glutathione, an antioxidant in biology. Thiyl radicals (sulfur-centred) can transform to carbon-centred radicals via hydrogen atom exchange equilibria. The formation of carbon-centred radicals could lead to protein damage via the formation of C−C bonds or backbone fragmentation.

    Because of the weakness of the S−H bond, thiols can function as scavengers of free radicals.

    Biological importance

    The catalytic cycle for ribonucleotide reductase, demonstrating the role of thiyl radicals in producing the genetic machinery of life.

    Cysteine and cystine

    As the functional group of the amino acid cysteine, the thiol group plays a very important role in biology. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of protein folding, an oxidation reaction can generate a cystine unit with a disulfide bond (−S−S−). Disulfide bonds can contribute to a protein's tertiary structure if the cysteines are part of the same peptide chain, or contribute to the quaternary structure of multi-unit proteins by forming fairly strong covalent bonds between different peptide chains. A physical manifestation of cysteine-cystine equilibrium is provided by hair straightening technologies.

    Sulfhydryl groups in the active site of an enzyme can form noncovalent bonds with the enzyme's substrate as well, contributing to covalent catalytic activity in catalytic triads. Active site cysteine residues are the functional unit in cysteine protease catalytic triads. Cysteine residues may also react with heavy metal ions (Zn2+, Cd2+, Pb2+, Hg2+, Ag+) because of the high affinity between the soft sulfide and the soft metal (see hard and soft acids and bases). This can deform and inactivate the protein, and is one mechanism of heavy metal poisoning.

    Drugs containing thiol group 6-Mercaptopurine (anticancer) Captopril (antihypertensive) D-penicillamine (antiarthritic) Sodium aurothiolate (antiarthritic)

    Cofactors

    Many cofactors (non-protein-based helper molecules) feature thiols. The biosynthesis and degradation of fatty acids and related long-chain hydrocarbons is conducted on a scaffold that anchors the growing chain through a thioester derived from the thiol Coenzyme A. The biosynthesis of methane, the principal hydrocarbon on Earth, arises from the reaction mediated by coenzyme M, 2-mercaptoethyl sulfonic acid. Thiolates, the conjugate bases derived from thiols, form strong complexes with many metal ions, especially those classified as soft. The stability of metal thiolates parallels that of the corresponding sulfide minerals.

    In skunks

    The defensive spray of skunks consists mainly of low-molecular-weight thiols and derivatives with a foul odor, which protects the skunk from predators. Owls are able to prey on skunks, as they lack a sense of smell.

    Examples of thiols

    Mathematical statistics

    From Wikipedia, the free encyclopedia
    Illustration of linear regression on a data set. Regression analysis is an important part of mathematical statistics.

    Introduction

    Statistical data collection is concerned with the planning of studies, especially with the design of randomized experiments and with the planning of surveys using random sampling. The initial analysis of the data often follows the study protocol specified prior to the study being conducted. The data from a study can also be analyzed to consider secondary hypotheses inspired by the initial results, or to suggest new studies. A secondary analysis of the data from a planned study uses tools from data analysis, and the process of doing this is mathematical statistics.

    Data analysis is divided into:

    • descriptive statistics – the part of statistics that describes data, i.e. summarises the data and their typical properties.
    • inferential statistics – the part of statistics that draws conclusions from data (using some model for the data): For example, inferential statistics involves selecting a model for the data, checking whether the data fulfill the conditions of a particular model, and with quantifying the involved uncertainty (e.g. using confidence intervals).

    While the tools of data analysis work best on data from randomized studies, they are also applied to other kinds of data. For example, from natural experiments and observational studies, in which case the inference is dependent on the model chosen by the statistician, and so subjective.

    Topics

    The following are some of the important topics in mathematical statistics:

    Probability distributions

    A probability distribution is a function that assigns a probability to each measurable subset of the possible outcomes of a random experiment, survey, or procedure of statistical inference. Examples are found in experiments whose sample space is non-numerical, where the distribution would be a categorical distribution; experiments whose sample space is encoded by discrete random variables, where the distribution can be specified by a probability mass function; and experiments with sample spaces encoded by continuous random variables, where the distribution can be specified by a probability density function. More complex experiments, such as those involving stochastic processes defined in continuous time, may demand the use of more general probability measures.

    A probability distribution can either be univariate or multivariate. A univariate distribution gives the probabilities of a single random variable taking on various alternative values; a multivariate distribution (a joint probability distribution) gives the probabilities of a random vector—a set of two or more random variables—taking on various combinations of values. Important and commonly encountered univariate probability distributions include the binomial distribution, the hypergeometric distribution, and the normal distribution. The multivariate normal distribution is a commonly encountered multivariate distribution.

    Special distributions

    Statistical inference

    Statistical inference is the process of drawing conclusions from data that are subject to random variation, for example, observational errors or sampling variation. Initial requirements of such a system of procedures for inference and induction are that the system should produce reasonable answers when applied to well-defined situations and that it should be general enough to be applied across a range of situations. Inferential statistics are used to test hypotheses and make estimations using sample data. Whereas descriptive statistics describe a sample, inferential statistics infer predictions about a larger population that the sample represents.

    The outcome of statistical inference may be an answer to the question "what should be done next?", where this might be a decision about making further experiments or surveys, or about drawing a conclusion before implementing some organizational or governmental policy. For the most part, statistical inference makes propositions about populations, using data drawn from the population of interest via some form of random sampling. More generally, data about a random process is obtained from its observed behavior during a finite period of time. Given a parameter or hypothesis about which one wishes to make inference, statistical inference most often uses:

    • a statistical model of the random process that is supposed to generate the data, which is known when randomization has been used, and
    • a particular realization of the random process; i.e., a set of data.

    Regression

    In statistics, regression analysis is a statistical process for estimating the relationships among variables. It includes many ways for modeling and analyzing several variables, when the focus is on the relationship between a dependent variable and one or more independent variables. More specifically, regression analysis helps one understand how the typical value of the dependent variable (or 'criterion variable') changes when any one of the independent variables is varied, while the other independent variables are held fixed. Most commonly, regression analysis estimates the conditional expectation of the dependent variable given the independent variables – that is, the average value of the dependent variable when the independent variables are fixed. Less commonly, the focus is on a quantile, or other location parameter of the conditional distribution of the dependent variable given the independent variables. In all cases, the estimation target is a function of the independent variables called the regression function. In regression analysis, it is also of interest to characterize the variation of the dependent variable around the regression function which can be described by a probability distribution.

    Many techniques for carrying out regression analysis have been developed. Familiar methods, such as linear regression, are parametric, in that the regression function is defined in terms of a finite number of unknown parameters that are estimated from the data (e.g. using ordinary least squares). Nonparametric regression refers to techniques that allow the regression function to lie in a specified set of functions, which may be infinite-dimensional.

    Nonparametric statistics

    Nonparametric statistics are values calculated from data in a way that is not based on parameterized families of probability distributions. They include both descriptive and inferential statistics. The typical parameters are the mean, variance, etc. Unlike parametric statistics, nonparametric statistics make no assumptions about the probability distributions of the variables being assessed.

    Non-parametric methods are widely used for studying populations that take on a ranked order (such as movie reviews receiving one to four stars). The use of non-parametric methods may be necessary when data have a ranking but no clear numerical interpretation, such as when assessing preferences. In terms of levels of measurement, non-parametric methods result in "ordinal" data.

    As non-parametric methods make fewer assumptions, their applicability is much wider than the corresponding parametric methods. In particular, they may be applied in situations where less is known about the application in question. Also, due to the reliance on fewer assumptions, non-parametric methods are more robust.

    One drawback of non-parametric methods is that since they do not rely on assumptions, they are generally less powerful than their parametric counterparts. Low power non-parametric tests are problematic because a common use of these methods is for when a sample has a low sample size. Many parametric methods are proven to be the most powerful tests through methods such as the Neyman–Pearson lemma and the Likelihood-ratio test.

    Another justification for the use of non-parametric methods is simplicity. In certain cases, even when the use of parametric methods is justified, non-parametric methods may be easier to use. Due both to this simplicity and to their greater robustness, non-parametric methods are seen by some statisticians as leaving less room for improper use and misunderstanding.

    Statistics, mathematics, and mathematical statistics

    Mathematical statistics is a key subset of the discipline of statistics. Statistical theorists study and improve statistical procedures with mathematics, and statistical research often raises mathematical questions.

    Mathematicians and statisticians like Gauss, Laplace, and C. S. Peirce used decision theory with probability distributions and loss functions (or utility functions). The decision-theoretic approach to statistical inference was reinvigorated by Abraham Wald and his successors, and makes extensive use of scientific computing, analysis, and optimization; for the design of experiments, statisticians use algebra and combinatorics. But while statistical practice often relies on probability and decision theory, their application can be controversial.

    Lie point symmetry

    From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Lie_point_symmetry     ...