Diphenylmethane is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

(C₆H₅)₂CH₂ (often abbreviated ). The compound consists of

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...

wherein two hydrogen atoms are replaced by two

phenyl group In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula , and is often represented by the symbol Ph (archaically φ) or Ø. The phenyl group is closely related to benzene and can be viewed as a benzene ...

s. It is a white solid. Diphenylmethane is a common

skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...

in organic chemistry. The diphenylmethyl group is also known as ''

benzhydryl The benzhydryl compounds are a group of organic compounds whose parent structure, parent structural formula, structures include diphenylmethane (which is two benzene rings connected by a single substituent#Methane substituents, methane), with any ...

''.

Synthesis

It is prepared by the Friedel–Crafts alkylation of benzyl chloride with

benzene Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...

in the presence of a

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

such as

aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are col ...

: :C₆H₅CH₂Cl + C₆H₆ → (C₆H₅)₂CH₂ + HCl

Reactivity of the C-H bond

The methylene group in diphenylmethane is mildly acidic with a p''K''_a of 32.2, and so can be deprotonated with

sodium amide Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the formula . It is a salt composed of the sodium cation and the azanide anion. This solid, which is dangerously reactive toward water, is whit ...

. :(C₆H₅)₂CH₂ + NaNH₂⁻ → (C₆H₅)₂CHNa + NH₃ The resulting

carbanion In organic chemistry, a carbanion is an anion with a lone pair attached to a tervalent carbon atom. This gives the carbon atom a negative charge. Formally, a carbanion is the conjugate base of a carbon acid: : where B stands for the base (chemist ...

can be alkylated. For example, treatment with ''n''-bromobutane produces 1,1-diphenylpentane in 92% yield. :(C₆H₅)₂CH⁻ + CH₃CH₂CH₂CH₂Br → (C₆H₅)₂CHCH₂CH₂CH₂CH₃ + Br⁻

Alkylation Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...

of various benzhydryl compounds has been demonstrated using the corresponding alkyl halides, both primary ( benzyl chloride, β-phenylethyl chloride, and n-octyl bromide) and secondary ( benzhydryl chloride, α-phenylethyl chloride, and

isopropyl chloride Isopropyl chloride is an organic compound with the chemical formula (CH3)2CHCl. It is a colourless to slightly yellow, volatile, flammable liquid with a sweet, ether-like (almost like petroleum) odour. It is used as an industrial solvent. It ...

), in yields between 86 and 99%. The acidity of the methylene group in diphenylmethane is due to the weakness of the (C₆H₅)₂CH–H bond, which has a

bond dissociation energy The bond-dissociation energy (BDE, ''D''0, or ''DH°'') is one measure of the strength of a chemical bond . It can be defined as the standard enthalpy change when is cleaved by homolysis to give fragments A and B, which are usually radical ...

of 82 kcal mol⁻¹ (340 kJ mol⁻¹). This is well below the published bond dissociation energies for comparable C–H bonds in

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

, where BDE((CH₃)₂CH–H)=98.6 kcal mol⁻¹, and

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...

, where BDE(C₆H₅CH₂–H)=89.7 kcal mol⁻¹.

Derivatives

A number of diphenylmethane

derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...

s are

antihistamine Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides ...

s and/or

anticholinergic Anticholinergics (anticholinergic agents) are substances that block the action of the acetylcholine (ACh) neurotransmitter at synapses in the central nervous system, central and peripheral nervous system. These agents inhibit the parasympatheti ...

s. These include captodiame,

diphenhydramine Diphenhydramine, sold under the brand name Benadryl among others, is an antihistamine and sedative. Although generally considered sedating, diphenhydramine can cause paradoxical central nervous system stimulation in some individuals, particula ...

, doxylamine, hydroxyzine, and pheniramine, among others.

References

Benzyl compounds {{Hydrocarbon-stub

Synthesis

Reactivity of the C-H bond

Derivatives

See also

References