Question

why
alc.KOH carries elimination
Whereas
Alk.KOH carries substitution​

Answer 1

Explanation:

In alcoholic solution, the KOH is basic enough (pKa=15.74) to deprotonate a small amount of the alcohol molecules (pKa=16–17), thus forming alkoxide salts (ROK). The alkoxide anions RO− are not only more basic than pure OH− but they are also bulkier (how much bulkier depends on the alkyl group). The higher bulkiness makes RO− a worse nucleophile than OH− and the higher basicity makes it better at E2 eliminations.

Answer 2

Answer:

In alcoholic solution, the KOH is basic enough (pka=15.74) to deprotonate a small amount of the alcohol molecules (pKa=16–17), thus forming alkoxide salts (ROK). The alkoxide anions RO are not only more basic than pure OH- but they are also bulkier (how much bulkier depends on the alkyl group). The higher bulkiness makes RO- a worse nucleophile than OH and the higher basicity makes it better at E2 eliminations.