Neophyl chloride
Encyclopedia
Neophyl chloride, C6H5C(CH3)2CH2Cl, is a halogenated organic compound
with unusual nucleophilic substitution properties. Neophyl chloride is used to form a versatile organolithium reagent
, neophyl lithium, by reaction with lithium.
with neophyl alcohol:
It is easily prepared on a large scale by combining benzene
and methallyl chloride in the presence of a catalytic
quantity of sulfuric acid
. The reaction is an example of an electrophilic aromatic substitution
.
Alternatively tert-butylbenzene can be chlorinated
with sulfuryl chloride
.
. Organolithium reagents are useful due to their nucleophilic
properties and their ability to form carbon to carbon bonds, like in reactions with carbonyl
s.
Neophyl chloride is of interest to organic chemists due to its substitution properties. Neophyl chloride is a neopentyl
halide
which means it is subject to the neopentyl effect. This effect makes SN2 nucleophilic substitution
highly unlikely because of steric interaction
s due to the branching of the β-carbon. No rotamer
of the molecule would allow a backside attack of the α carbon.
β-Hydride elimination
also does not occur with neophyl derivatives as this group lacks hydrogens at the β positions. These factors make neophyl chloride a precursor to intermediates that resist common substitution and elimination reaction
s.
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with unusual nucleophilic substitution properties. Neophyl chloride is used to form a versatile organolithium reagent
Organolithium reagent
An organolithium reagent is an organometallic compound with a direct bond between a carbon and a lithium atom. As the electropositive nature of lithium puts most of the charge density of the bond on the carbon atom, effectively creating a carbanion, organolithium compounds are extremely powerful...
, neophyl lithium, by reaction with lithium.
Preparation
Neophyl chloride was first synthesized by Haller and Ramart by reacting the chlorinating reagent thionyl chlorideThionyl chloride
Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. Thionyl chloride is sometimes confused with sulfuryl...
with neophyl alcohol:
- C6H5C(CH3)2CH2OH + SOCl2 → C6H5C(CH3)2CH2Cl + HCl + SO2
It is easily prepared on a large scale by combining benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
and methallyl chloride in the presence of a catalytic
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
quantity of sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
. The reaction is an example of an electrophilic aromatic substitution
Electrophilic aromatic substitution
Electrophilic aromatic substitution EAS is an organic reaction in which an atom, usually hydrogen, appended to an aromatic system is replaced by an electrophile...
.
- H2C=C(CH3)2CH2Cl + C6H6 → C6H5C(CH3)2CH2Cl
Alternatively tert-butylbenzene can be chlorinated
Chlorination
Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water...
with sulfuryl chloride
Sulfuryl chloride
Sulfuryl chloride is an inorganic compound with the formula SO2Cl2. At room temperature, it is a colorless liquid with a pungent odor. Sulfuryl chloride is not found in nature, as can be inferred from its rapid hydrolysis....
.
Reactions and applications
Neophyl chloride can be used to form an organolithium reagent, neophyl lithium, by reaction with lithiumLithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
. Organolithium reagents are useful due to their nucleophilic
Nucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...
properties and their ability to form carbon to carbon bonds, like in reactions with carbonyl
Carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups....
s.
- C6H5C(CH3)2CH2Cl + Li → C6H5C(CH3)2CH2Li
Neophyl chloride is of interest to organic chemists due to its substitution properties. Neophyl chloride is a neopentyl
Neopentane
Neopentane, also called dimethylpropane, is a double-branched-chain alkane with five carbon atoms. Neopentane is an extremely flammable gas at room temperature and pressure which can condense into a highly volatile liquid on a cold day, in an ice bath, or when compressed to a higher...
halide
Halide
A halide is a binary compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. Many salts are halides...
which means it is subject to the neopentyl effect. This effect makes SN2 nucleophilic substitution
Nucleophilic substitution
In organic and inorganic chemistry, nucleophilic substitution is a fundamental class of reactions in which an electron nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms called the leaving group; the positive or partially positive...
highly unlikely because of steric interaction
Steric effects
Steric effects arise from the fact that each atom within a molecule occupies a certain amount of space. If atoms are brought too close together, there is an associated cost in energy due to overlapping electron clouds , and this may affect the molecule's preferred shape and reactivity.-Steric...
s due to the branching of the β-carbon. No rotamer
Conformational isomerism
In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted exclusively by rotations about formally single bonds...
of the molecule would allow a backside attack of the α carbon.
β-Hydride elimination
Beta-hydride elimination
Beta-hydride elimination is a reaction in which an alkyl group bonded to a metal centre is converted into the corresponding metal-bonded hydride and an alkene. The alkyl must have hydrogens on the beta carbon. For instance butyl groups can undergo this reaction but methyl groups cannot...
also does not occur with neophyl derivatives as this group lacks hydrogens at the β positions. These factors make neophyl chloride a precursor to intermediates that resist common substitution and elimination reaction
Elimination reaction
An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism...
s.