Which of the following compounds is classified as an allylic alcohol?

• A. ${\mathrm{CH}}_2$=$\mathrm{CH}$-$\mathrm{OH}$
• B. ${\mathrm{CH}}_3$-$\mathrm{CH}$($\mathrm{OH}$)-${\mathrm{CH}}_3$
• C. ${\mathrm{CH}}_3$-$\mathrm{CH}$=$\mathrm{CH}$$\mathrm{OH}$
• D. ${\mathrm{CH}}_2$=$\mathrm{CH}$-${\mathrm{CH}}_2$$\mathrm{OH}$

Answer: (D)

Verified step by step guidance

1. Understand the definition of an allylic alcohol: it is an alcohol where the hydroxyl group (-OH) is attached to a carbon atom that is adjacent (allylic position) to a carbon-carbon double bond (C=C).
2. Examine each compound to identify the position of the -OH group relative to any double bonds present.
3. For the first compound, \(CH_2=CH-OH\), the -OH is directly attached to the carbon involved in the double bond, so it is a vinyl alcohol, not allylic.
4. For the second compound, \(CH_3-CH(OH)-CH_3\), there is no double bond present, so it cannot be allylic.
5. For the third compound, \(CH_3-CH=CH-CH_2OH\), the -OH is on the carbon next to the double bond (the \(CH_2\) group adjacent to \(CH=CH\)), which fits the definition of an allylic alcohol.