here's a nice one.

this's easy , yet one important thing is hidden rest is routine.

2 pentyne gives 1 pentyne? how come how come?

yup and further it should not be a problem. :) gud tapan. but it can be a guess also . otherwise , no possibilty of reaction , anyways nice guess. or If you know it good .

complete this no ?

NOPES SRI, it wasnt a guess buddy!

1pentyne + KOH --> 2-pentyne........

and its NaNH2 for this one!!! [1]

ANS = 3-Octyne??

pl. chk da answer sri

(2-Pentyne) H₃C-CH₂-C ≡ C-CH₃ -----^(NaNH₂)----->(A) H₃C-CH₂-CH₂-C ≡ CH ------^(CH₃Cl)------->(B) H₃C-CH₂-CH₂-C ≡ C-CH₃ ------^(NaNH₂)---->
(C) H₃C-CH₂-CH₂-CH₂-C ≡ CH -------^{(CH₃CH₂Cl)}------->(D) H₃C-CH₂-CH₂-CH₂-C ≡ C-CH₂-CH₃ (3-Octyne)