I was looking at the organic chemistry 8th Ed textbook by Paula Yurknais Brucie. On page 509, I found this:

enter image description here

I think about it for a while and I am doubting that it is wrong. I believe the hydride ion itself cannot act as a nucleophile for SN2. (not really sure but I guess it is too small and too basic to work as a nucleophile, it should be much easier to attack hydrogen rather than carbon for hydride ion)

Is this reaction is possible with $\ce{NaH}$ in solvents other than water and alcohol? If so, how does the hydride ion open the epoxide ring? (hoping for an answer with mechanism)

And I am specifically talking about hydride ion (or hydrogen anion). Not sodium borohydride $\ce{NaBH4}$, lithium aluminum hydride $\ce{LiAlH4}$, or other metal hydrides.

  • 1
    $\begingroup$ Well, there's no proton acidic enough, so it's gonna open the ring. $\endgroup$
    – Mithoron
    Aug 21 at 18:14
  • $\begingroup$ Going to have to be in aprotic solvent. NaH reacts vigourously with alcohols and water $\endgroup$
    – Waylander
    Aug 21 at 20:00
  • 8
    $\begingroup$ I have been looking for this reaction and I find no examples. Nor in my limited experience of 40+ years can I ever recall seeing sodium hydride used as a source of nucleophilic hydride without some modifying agent (such as this example sciencedirect.com/science/article/abs/pii/S0040403900986313). Perhaps someone who has better database access than I can find it. $\endgroup$
    – Waylander
    Aug 21 at 20:47
  • 4
    $\begingroup$ @Mithoron I don't think so. It is going to sit there and do nothing until it is worked up. $\endgroup$
    – Waylander
    Aug 22 at 19:12
  • 2
    $\begingroup$ @MathewMahindaratne the answer you refer to concerns LiAlH4 opening of epoxides. It specifically excludes any reference to NaH even though the OP asked about NaH. $\endgroup$
    – Waylander
    Sep 1 at 10:24

Further to my comments above, I am going to offer my opinion that the book is wrong and the epoxide is not opened by sodium hydride as depicted. I have failed to find any literature examples of such a reaction and, in 40+ years as a synthetic chemist, I can recall no reactions in which $\ce{NaH}$, unmodified by other reagents, acts as a source of nucleophilic $\ce{H-}$.

Can anyone produce a literature example?

  • $\begingroup$ @user55119 do you know of any examples? $\endgroup$
    – Waylander
    Aug 25 at 9:56
  • 3
    $\begingroup$ I was as nonplussed as you when I saw this reaction of "naked" NaH. In my 40++ years I have not seen such a transformation. My Chem. Absts. search turned up only the reference in your Comment (DOI:10.1016/S0040-4039(00)98631-3). Textbooks are invariably riddled with errors and omissions. $\endgroup$
    – user55119
    Aug 25 at 16:13
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    $\begingroup$ Apropos of my final remark above, I once used a textbook that interpreted in great detail the fragmentation pattern of the EI mass spectrum of methyl propyl ether. Only one problem. The spectrum was that of diethyl ether! $\endgroup$
    – user55119
    Aug 25 at 23:20
  • $\begingroup$ @Waylander, maybe the textbook is incorrect and just makes up this reaction out of nowhere. I also cannot found any example in the literature. Thanks for the answer. $\endgroup$ Aug 26 at 12:26
  • $\begingroup$ Kicked it around this evening at the pub with a synthetic chemistry colleague of similar experience - he also thinks this reaction will not occur. $\endgroup$
    – Waylander
    Aug 27 at 17:44

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