Diphenylmethane

Diphenylmethane is an organic compound with the formula (C₆H₅)₂CH₂ (often abbreviated CH
₂Ph
₂). The compound consists of methane wherein two hydrogen atoms are replaced by two phenyl groups. It is a white solid.

Diphenylmethane

Names
Preferred IUPAC name 1,1′-Methylenedibenzene[1]
Other names Diphenylmethane Benzylbenzene
Identifiers
CAS Number	101-81-5 Y
3D model (JSmol)	Interactive image
Abbreviations	BnPh, Ph2CH2
ChEBI	CHEBI:38884 Y
ChEMBL	ChEMBL1796022 N
ChemSpider	7299 Y
ECHA InfoCard	100.002.708
MeSH	Diphenylmethane
PubChem CID	7580
UNII	K3E387I0BC N
CompTox Dashboard (EPA)	DTXSID1041891
InChI InChI=1S/C13H12/c1-3-7-12(8-4-1)11-13-9-5-2-6-10-13/h1-10H,11H2 Y Key: CZZYITDELCSZES-UHFFFAOYSA-N Y InChI=1/C13H12/c1-3-7-12(8-4-1)11-13-9-5-2-6-10-13/h1-10H,11H2 Key: CZZYITDELCSZES-UHFFFAOYAV
SMILES c1c(cccc1)Cc2ccccc2
Properties
Chemical formula	C13H12
Molar mass	168.234
Appearance	colourless oil
Density	1.006 g/mL
Melting point	22 to 24 °C (72 to 75 °F; 295 to 297 K)
Boiling point	264 °C (507 °F; 537 K)
Solubility in water	14 mg/L
Acidity (pKa)	32.2
Magnetic susceptibility (χ)	−115.7·10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	flammable
Flash point	> 110 °C; 230 °F; 383 K
Related compounds
Related compounds	Diphenylmethanol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Diphenylmethane is a common skeleton in organic chemistry. The diphenylmethyl group is also known as benzhydryl.

Synthesis

It is prepared by the Friedel–Crafts alkylation of benzyl chloride with benzene in the presence of a Lewis acid such as aluminium chloride:^[2]

C₆H₅CH₂Cl + C₆H₆ → (C₆H₅)₂CH₂ + HCl

Reactivity of the C-H bond

The methylene group in diphenylmethane is mildly acidic with a pK_a of 32.2, and so can be deprotonated with sodium amide.^[3]

(C₆H₅)₂CH₂ + NaNH₂⁻ → (C₆H₅)₂CHNa + NH₃

The resulting carbanion can be alkylated. For example, treatment with n-bromobutane produces 1,1-diphenylpentane in 92% yield.^[4]

(C₆H₅)₂CH⁻ + CH₃CH₂CH₂CH₂Br → (C₆H₅)₂CHCH₂CH₂CH₂CH₃ + Br⁻

Alkylation 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), in yields between 86 and 99%.^[3][4]

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 of 82 kcal mol⁻¹ (340 kJ mol⁻¹).^[5] This is well below the published bond dissociation energies for comparable C–H bonds in propane, where BDE((CH₃)₂CH–H)=98.6 kcal mol⁻¹, and toluene, where BDE(C₆H₅CH₂–H)=89.7 kcal mol⁻¹.^[6][7]

Derivatives

A number of diphenylmethane derivatives are antihistamines and/or anticholinergics. These include captodiame, diphenhydramine, doxylamine, hydroxyzine, and pheniramine, among others.

See also

• Benzhydryl compounds
• Toluene (methylbenzene, phenylmethane)
• Triphenylmethane
• Tetraphenylmethane