organic synthesis and C-C bond formation

Question 1

how do we increase the length of a carbon chain in synthesis?

Answer 1

by adding a nitrile (CN)

Question 2

how do we make HCN in situ? give the equation

Answer 2

NaCN + H2SO4 ———> HCN + NaHSO4

Question 3

hydrogenation of nitriles

Answer 3

nitrile + 2H2 ———> amine
nickel catalyst

Question 4

hydration of nitriles

Answer 4

nitrile + H2O + HCl ———> carboxylic acid + ammonium salt