How is an alkane made from #"3-hexyne"#?

1 Answer
anor277
Oct 30, 2017

Well, you gots an acetylene derivative.....

Explanation:

....the which, I presume, is REDUCED by alkali metal in liquid ammonia to give A TRANS olefin...(there is a name for this reaction I think, I lent out my organic text so at the moment I am ignorant)

And so.....starting with #"3-hexyne"....#

#"H"_3"CCH"_2"C"-="CCH"_2"CH"_3stackrel(Na,NH_3(l))rarr"#

We get #"trans-3-hexene"#

#trans-"H"_3"CCH"_2"HC=CHCH"_2"CH"_3#

And the second reaction gives 1,2 addition across the olefin bond to deuterium labels.....

#trans-"H"_3"CCH"_2"HC=CHCH"_2"CH"_3stackrel(D_2)rarr#

#"H"_3C-CH_2dotCH(D)dotCH(D)CH_2CH_3#

Carbons three and four as indicated are potentially chiral.....and cis addition of #""^2H_2#, as is necessitated by the conditions of the reaction, i.e. on a surface would lead to to #R,R# and #S,S# enantiomers, and not the #R,S# product......

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