Give the major product obtained from the reaction of each

Solution:

Here we have to write the major product obtained from the reaction of each of the following with excess HCI.

a. CH3CH2C≡CH

b. CH3CH2C≡CCH2CH3

c. CH3CH2C≡CCH2CH2CH3

Here all the reactants are alkyne and we have to add with HCl. The mechanism of the reaction is electrophilic substitution reaction. These reactions has been carried out by Markovnikov's rule.

Markovnikov's rule (Markovnikov addition):-

Markovnikov's rule is  an addition reaction of a protic acid HX (hydrogen chloride, hydrogen bromide, or hydrogen iodide) to an alkene or alkyne. In this reaction the hydrogen atom of HX becomes bonded to the carbon atom that had the greatest number of hydrogen atoms in the starting alkene or alkyne and the product which has greater %  of yield is considered as the major product.

Step 1

(a)

In this reaction the Cl- ion of HCl is act as an electrophile. On addition of excess HCl with butyne form 2,2-dichloro butane as the major product.

CH3CH2C≡CH      

                        (butyne)                                     (2,2-dichloro butane)