Diphenylmethane

Diphenylmethane
Names
Preferred IUPAC name
1,1′-Methylenedibenzene[1]
Other names
Diphenylmethane
Benzylbenzene
Identifiers
3D model (JSmol)
Abbreviations BnPh, Ph2CH2
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.002.708 Edit this at Wikidata
MeSH Diphenylmethane
UNII
  • InChI=1S/C13H12/c1-3-7-12(8-4-1)11-13-9-5-2-6-10-13/h1-10H,11H2 checkY
    Key: CZZYITDELCSZES-UHFFFAOYSA-N checkY
  • InChI=1/C13H12/c1-3-7-12(8-4-1)11-13-9-5-2-6-10-13/h1-10H,11H2
    Key: CZZYITDELCSZES-UHFFFAOYAV
  • c1c(cccc1)Cc2ccccc2
Properties
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)
14 mg/L
Acidity (pKa) 32.2
-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 checkY☒N ?)

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 pKa 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]

See also

References

  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.
  3. ^ 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.
  4. ^ 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.
  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.
  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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