Question

Is alcohol acid or base?

Answer 1

Alcohol is an organic compound that carries at least one hydroxyl functional group $( - OH)$ bound to a saturated carbon atom. The general formula for alcohol is ${C_n}{H_{2n + 1}}OH$ . Primary alcohol includes $(RC{H_2}OH)$ , secondary alcohols $({R_2}CHOH)$ and tertiary alcohols $({R_3}COH)$ .

Complete answer:
We measure acidity using a term called $p{K_a}$ . This is a measure of the equilibrium constant for a species giving up a proton to form its conjugate base. $p{K_a}$ is on a scale of about $- 10$ to $50$ . The higher the $p{K_a}$ the less acidic it is. Lower $p{K_a}$ (more negative) $=$ more acidic. Water $(p{K_a} = 15.7)$ is a weaker acid than $HCL$ $(p{K_a} = - 8)$ . The stronger the acid, the weaker the conjugate base. The weaker the acid, the stronger the conjugate base.
By the Arrhenius Definition of an acid and base, alcohol is neither acidic nor basic when dissolved in water, as it neither produces ${H^ + }$ nor $O{H^ - }$ In the solution.
Alcohol with a $p{K_a}$ of around $16 - 19$ , they are in general, slightly weaker acids than water. With strong bases such as sodium hydroxide or sodium they form salts called alkoxides, with the general formula $R{O^ - }{M^ + }$ .
The acidity of alcohol is strongly affected by solvation. In the gas phase, alcohols are more acidic than in water. The acid ionization constant $(Ka)$ of ethanol is about $10 \sim 18$ slightly less than that of water. Ethanol can be converted to its conjugate base by the conjugate base of a weaker acid such as ammonia
${C_2}{H_5}OH + NaN{H_2} \rightleftarrows {C_2}{H_5}{O^ - }N{a^ + } + N{H_3}$ . The order of various liquid alcohols generally in water $>$ primary $>$ secondary $>$ tertiary. In gas phase the order of acidity is reversed.
Primary alcohols can be oxidized either to aldehydes $(R - CHO)$ or to carboxylic acids $(R - C{O_2}H)$ ,tertiary alcohols are resistant to oxidation. The direct oxidation of primary alcohols to carboxylic acids normally proceed via the corresponding aldehyde, by further oxidation to the carboxylic acid.
Because of hydrogen bonding, alcohols tend to have higher boiling points than comparable hydrocarbons and ether. The boiling point of the alcohol ethanol is $78.29^\circ$ C, compared to $69^\circ$ C for the hydrocarbon hexane, and $34.6^\circ$ C for diethyl ether.

Note:
The hydroxyl group makes alcohol polar. Owing to the presence of the polar $OH$ alcohols are more water soluble than simple hydrocarbons. Methanol, ethanol and propanol are miscible in water. Butanol with a four carbon chain, is moderately soluble.