Question

Idenify a reagent from the following list which can easily distinguish between 1-butyne and 2-butyne
A. Bromine , `C Cl_4`
B. `H_2`, Lindlar catalyst
C. Dilute `H_2SO_4, HgSO_4`
D. Ammonical `Cu_2Cl_2` solution

Answer 1

Correct Answer - D
In butyne-1, acidic hydrogen is present while in butyne-2 acidic hydrogen is not present, so butyne-1 give red ppt. with ammonical `Cu_2Cl_2` solutions, while butyne-2 does not give these ppt.
`underset"butyne-1"(2CH_3-CH_2-C)-=CH+Cu_2Cl_2+2NH_4OH to underset"red ppt."(2CH_3-CH_2)-C-=C.Cu darr +2NH_4Cl +2H_2O`
`CH_3-C-=C-CH_3+Cu_2Cl_2+2NH_4OH to ` No reaction