Benzyl Alcohol Infrared Spectrum

Benzyl alcohol Infrared spectrum has peaks for O—H and sp C—H lacks peak for C=0... 

The broad, intense absorption at 3300 cm-1 is attributable to a hydroxyl group. Although both phenol and benzyl alcohol are possibilities, the peaks at 2800-2900 cm-1 reveal the presence of hydrogen bonded to -hybridized carbon. All carbons are sp2-hybridized in phenol. The infrared spectrum is that of benzyl alcohol. 

In 23-dihydroxypyrazine and derivatives Honzl (853), from measurements of infrared spectra in chloroform and ultraviolet spectra in aqueous alcohol, has proposed that 5,6-dichloro-l-cyclohexyl-3-hydroxy-2-oxo-l, 2-dihydropyrazine (pA in water 4.66, 5.66) exists in the form (48). The p.m.r. spectra of some 5- and 6-methyl- and 5- and 6-phenyl-2,3-dihydroxypyrazines have been reported (483). In the 2,5-dihydroxypyrazine series, the infrared spectrum (Nujol) of 2-benzyl-3,6-dihydroxy-5-methylpyrazine has been interpreted as indicating that the major tautomeric form present in the solid state was the dihydroxy form (49), but the ultraviolet spectrum in ethanol was considered consistent with the coexistence of the dihydroxy (49) and oxo-hydroxy form, for example, (50), Although the structure (51) has been proposed for 3-butyl-2,5-dihydroxypyrazine (1092), the evidence in favor of this structure is inconclusive. 

Some allylic and benzylic alcohols give this test result because the reagent can oxidize them to aldehydes and ketones, which subsequently react. Some alcohols may be contaminated with carbonyl impurities, either as a result of their method of synthesis (reduction) or as a result of their becoming air-oxidized. A precipitate formed from small amounts of impurity in the solution will be formed in small amounts. With some caution, a test that gives only a slight amount of precipitate can usually be ignored. The infrared spectrum of the compound should establish its identity and identify any impurities present. 

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