Question

The acidic character of $1^o,2^o,3^o$ alcohols, $H_{2}O$ and $RC\equiv CH$ is of the order:

• A. $H_{2}O>1^o>2^o>3^o>RC\equiv CH$
• B. $RC\equiv CH>3^o>2^o>1^o>H_{2}O$
• C. $1^o>2^o>3^o>H_{2}O>RC\equiv CH$
• D. $3^o>2^o>1^o>H_{2}O>RC\equiv CH$

Answer 1

The correct option is A $H_{2}O>1^o>2^o>3^o>RC\equiv CH$

The $+I$ electron releasing effect of alkyl group decreases the acidic strength of hydrogen and makes tertiary alcohol less acidic than secondary and primary alcohol. Water with no inductive effect is more acidic. The $C$ in terminal alkyne is $sp$ hybridized and thus more electronegative. Electronegative atoms adjacent to the charge will stabilize the charge. $+I$ effect destabilize the negative charge. Overall it is least acidic. The order of acidic strength $H_{2}O>1^o>2^o>3^o>RC\equiv CH$