Diphenylmethane

Diphenylmethane
Names
	Preferred IUPAC name 1,1′-Methylenedibenzene
	Other names Diphenylmethane; Benzylbenzene
Identifiers
CAS Number	101-81-5 ;
3D model (JSmol)	Interactive image;
Abbreviations	BnPh, Ph2CH2
ChEBI	CHEBI:38884 ;
ChEMBL	ChEMBL1796022 ;
ChemSpider	7299 ;
ECHA InfoCard	100.002.708
MeSH	Diphenylmethane
PubChem CID	7580;
UNII	K3E387I0BC ;
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 Key: CZZYITDELCSZES-UHFFFAOYSA-N ; 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). verify (what is ?) Infobox references

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 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]

References

^ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 452. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
^ W. W. Hartman and Ross Phillips (1934). "Diphenylmethane". Organic Syntheses. 14: 34. doi:10.15227/orgsyn.014.0034.
^ ^a ^b Hauser, Charles R.; Hamrick, Phillip J. (1957). "Alkylation of Diphenylmethane with Alkyl Halides by Sodium Amide. Substitution versus β-Elimination. Relative Acidities of Diphenylmethane and Ammonia". J. Am. Chem. Soc. 79 (12): 3142–3145. doi:10.1021/ja01569a041.
^ ^a ^b Murphy, William S.; Hamrick, Phillip J.; Hauser, Charles R. (1968). "1,1-Diphenylpentane". Organic Syntheses. 48: 80. doi:10.15227/orgsyn.048.0080.
^ Zhang, Xian-Man; Bordwell, Frederick G. (1992). "Homolytic bond dissociation energies of the benzylic carbon-hydrogen bonds in radical anions and radical cations derived from fluorenes, triphenylmethanes, and related compounds". J. Am. Chem. Soc. 114 (25): 9787–9792. doi:10.1021/ja00051a010.
^ Blanksby, S. J.; Ellison, G. B. (2003). "Bond Dissociation Energies of Organic Molecules". Accounts of Chemical Research. 36 (4): 255–263. doi:10.1021/ar020230d. PMID 12693923.
^ Streitwieser, Andrew; Bergman, Robert G. (2018). "Table of Bond Dissociation Energies". University of California, Berkeley. Retrieved December 30, 2021.

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[1] International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 452. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.

[2] W. W. Hartman and Ross Phillips (1934). "Diphenylmethane". Organic Syntheses. 14: 34. doi:10.15227/orgsyn.014.0034.

[HauserJACS-3] Hauser, Charles R.; Hamrick, Phillip J. (1957). "Alkylation of Diphenylmethane with Alkyl Halides by Sodium Amide. Substitution versus β-Elimination. Relative Acidities of Diphenylmethane and Ammonia". J. Am. Chem. Soc. 79 (12): 3142–3145. doi:10.1021/ja01569a041.

[1,1-diphenylpentane-4] Murphy, William S.; Hamrick, Phillip J.; Hauser, Charles R. (1968). "1,1-Diphenylpentane". Organic Syntheses. 48: 80. doi:10.15227/orgsyn.048.0080.

[5] Zhang, Xian-Man; Bordwell, Frederick G. (1992). "Homolytic bond dissociation energies of the benzylic carbon-hydrogen bonds in radical anions and radical cations derived from fluorenes, triphenylmethanes, and related compounds". J. Am. Chem. Soc. 114 (25): 9787–9792. doi:10.1021/ja00051a010.

[BDE-6] Blanksby, S. J.; Ellison, G. B. (2003). "Bond Dissociation Energies of Organic Molecules". Accounts of Chemical Research. 36 (4): 255–263. doi:10.1021/ar020230d. PMID 12693923.

[7] Streitwieser, Andrew; Bergman, Robert G. (2018). "Table of Bond Dissociation Energies". University of California, Berkeley. Retrieved December 30, 2021.

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Synthesis

Reactivity of the C-H bond

See also

References