The structure of the adduct can be determined on the basis of electrophilic addition of the reagent $NO ^{+} Cl ^{-}$to the alkene. The reaction proceeds in accordance with Markovnikov's rule, where in, the negative part (i.e., $Cl ^{-}$) of the reagent is added to the carbon atom having lesser number of hydrogen atoms and the positive part goes to the carbon having more number of hydrogen atoms.
$CH_3 - CH = CH_2 + NOCl \rightarrow CH_3 - \underset{\overset{|}{C}l}{CH} - \underset{\overset{|}{NO}}{CH_2}$
(i) $NOCl \rightleftharpoons NO^+ + Cl^-$
(ii) $CH_3 - CH = CH_2 + NO^+ \rightarrow CH_3 - CH - \underset{\overset{|}{N}O}{CH_2}$
(stable carbocation)
