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The Atherton-Todd reaction is a
First, a tertiary amine is used to cleave a methyl group of dimethyl phosphite. The intermediate 1 results from this reaction step.
Subsequently, the intermediate 1 deprotonates the starting compound dimethylphosphite, so that intermediates 2a and intermediates 2b are formed. The intermediate 1 is then regenerated from the intermediate 2a.
Finally, intermediate 2b is chlorinated by tetrachloromethane and dimethyl chlorophosphate 3 is formed.
name reaction
A name reaction (or named reaction) is a chemical reaction named after its discoverer(s) or developer(s). Among the tens of thousands of organic reactions that are known, hundreds of such reactions are typically identified by the eponym. Well-know ...
in organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...
, which goes back to the British chemists F. R. Atherton, H. T. Openshaw and A. R. Todd. These described the reaction for the first time in 1945 as a method of converting dialkyl phosphites into dialkyl chlorophosphates. The dialkyl chlorophosphates formed are often too reactive to be isolated, though. For this reason, the synthesis of phosphates
Phosphates are the naturally occurring form of the element phosphorus.
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphor ...
or phosphoramidates can follow the Atherton-Todd reaction in the presence of alcohol
Alcohol may refer to:
Common uses
* Alcohol (chemistry), a class of compounds
* Ethanol, one of several alcohols, commonly known as alcohol in everyday life
** Alcohol (drug), intoxicant found in alcoholic beverages
** Alcoholic beverage, an alco ...
s or amines
In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
. The following equation gives an overview over the Atherton-Todd reaction using the reactant dimethyl phosphite as an example:
The reaction takes place after the addition of tetrachloromethane
Carbon tetrachloride, also known by many other names (such as carbon tet for short and tetrachloromethane, also IUPAC nomenclature of inorganic chemistry, recognised by the IUPAC), is a chemical compound with the chemical formula CCl4. It is a n ...
and a base. This base is usually a primary, secondary or tertiary amine
In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
. Instead of methyl groups other alkyl
In organic chemistry, an alkyl group is an alkane missing one hydrogen.
The term ''alkyl'' is intentionally unspecific to include many possible substitutions.
An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...
or benzyl groups may be present.
Reaction mechanism
A possible reaction mechanism for the Atherton-Todd reaction is presented here for the example of dimethylphosphite, just like in the overview reaction:
First, a tertiary amine is used to cleave a methyl group of dimethyl phosphite. The intermediate 1 results from this reaction step.
Subsequently, the intermediate 1 deprotonates the starting compound dimethylphosphite, so that intermediates 2a and intermediates 2b are formed. The intermediate 1 is then regenerated from the intermediate 2a.
Finally, intermediate 2b is chlorinated by tetrachloromethane and dimethyl chlorophosphate 3 is formed.
Possible subsequent reactions
After the synthesis of the dimethyl chlorophosphate, a further reaction (for example with a primary amine likeaniline
Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...
) is possible by the following reaction equation:
Atom economy
In this reaction, in addition to the starting compound dialkyl phosphite, tetrachloromethane and a base (an amine) are used instoichiometric
Stoichiometry () is the relationships between the masses of reactants and products before, during, and following chemical reactions.
Stoichiometry is based on the law of conservation of mass; the total mass of reactants must equal the total m ...
amounts. Only chloroform, which occurs after two reaction steps from tetrachloromethane, is relevant as a waste product for the assessment of the atomic economy. It should furthermore be kept in mind that the product of the reaction has a greater molar mass
In chemistry, the molar mass () (sometimes called molecular weight or formula weight, but see related quantities for usage) of a chemical substance ( element or compound) is defined as the ratio between the mass () and the amount of substance ...
than the starting compound. The atom economy
Atom economy (atom efficiency/percentage) is the conversion efficiency of a chemical process in terms of all atoms involved and the desired products produced. The simplest definition was introduced by Barry Trost in 1991 and is equal to the rati ...
of this reaction can therefore be classified as relatively good.
See also
The Atherton-Todd reaction is related to theAppel reaction
The Appel reaction is an organic reaction that converts an alcohol into an alkyl chloride using triphenylphosphine and carbon tetrachloride. The use of carbon tetrabromide or bromine as a halide source will yield alkyl bromides, whereas using car ...
. In the Appel reaction, tetrachloromethane is used for chlorination as well.
References