Directions : In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:
Which of the following can be used to distinguish between 1-butyne and 2-butyne? (1) Grignard reagent (2) Ammoniacal\[AgN{{O}_{3}}\] (3) Ammoniacal\[C{{u}_{2}}C{{l}_{2}}\] (4) Baeyefs reagentA) 1, 2 and 3 are correct
B) 1 and 2 are correct
C) 2 and 4 are correct
D) 1 and 3 are correct
Correct Answer: A
Solution :
1-butyne being a terminal alkyne has an acidic hydrogen and hence, reacts with Grignard reagent, ammoniacal\[AgN{{O}_{3}}\]and ammoniacal \[C{{u}_{2}}C{{l}_{2}}\]as follows \[\underset{1\,butyne}{\mathop{C{{H}_{3}}C{{H}_{2}}C\equiv CH}}\,+RMgX\xrightarrow{{}}\] \[RH+MgX(C\equiv CC{{H}_{2}}C{{H}_{3}})\] \[\underset{1\,-butyne}{\mathop{C{{H}_{3}}C{{H}_{2}}C\equiv CH}}\,+\underset{ammoniacal}{\mathop{AgN{{O}_{3}}}}\,\xrightarrow{{}}\] \[\underset{white\text{ }ppt}{\mathop{C{{H}_{3}}C{{H}_{2}}C\equiv CAg}}\,\] \[\underset{1\,-butyne}{\mathop{C{{H}_{3}}C{{H}_{2}}C\equiv CH}}\,+\underset{ammoniacal}{\mathop{C{{u}_{2}}C{{l}_{2}}}}\,\xrightarrow{{}}\] \[\underset{red\,ppt}{\mathop{C{{H}_{3}}C{{H}_{2}}C\equiv CCu}}\,\] However, 2-butyne because of the absence of acidic H-atom, does not give these reactions. Thus, these reagents are used to distinguish 1-butyne and 2-butyne. With Baeyer's reagent 1-butyne and 2-butyne both react as both are unsaturated compounds.
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