The New Clayden pp. 970 – 1002

p. 970 — The authors missed a bet in not discussing why  it takes so much more free energy to break HCl into ions (1347 kiloJoules) than into radicals (431 kiloJoules) — charge separation.  Another missed opportunity was not discussing  just how high the energetic penalty really is for charge separation, and the crucial role of solvent in moderating it. 

p. 971 — To be noted is that fact at all bond strengths in the book (and the literature) are for the free energy required to break the bond into neutral elements (e.g. radicals). 

p. 974 — “electron celibataire”  Y’alors, how I love ze French ! ! !   Shades of Dominique Strauss-Kahn.   What do you expect of a language that divides nouns into masculine and feminine?  LGBT is sure to protest. 

p. 983 — “We expect you to be mildly horrified by the inadequacy of the mechanism above.  But, unfortunately, we can’t do much better because no-one really knows quite what is happening.”   Good to have a confession of less than omnipotence.  Whenever I see something with a transition metal involved, I always wonder, why this particular one?  The McMurry reaction uses titanium, why not Vanadium, why not Scandium? 

p. 994 — “The Sn-C bond is relatively weak”  – All sorts of numerical bond strengths have been given in this chaper (good !), why not give this one? 

Again, irrelevant to Clayden, but not to chemistry.  An interesting article in the 14 Sep  Science (vol. 337 pp. 1322 – 1325 ’12) used a ‘fenced’ porphyrin manganese chloro compound to perform selective aliphatic C – H fluorination of a variety of natural products.  Hopefully the chapter on Organometallic chemistry coming up in 80 pages or so will explain all this.  Given the way the orbitals on S, P, Si have been discussed so far,  I doubt it.  Hopefully the organometallic chemistrhy chapter will be up to the level of the exquisite stereochemistry of fragmentation reactions described in the previous chapter.

p. 997 — Although the term frontier molecular orbital is used in the book, it is never explicitly defined.  You are told to look at the definition of LUMO, HOMO in the index — p. 111 — and their various uses, but the term doesn’t appear there. 

Again, although the MO in LUMO, HOMO, SOMO   stands for molecular orbitals, BUT if you really  look at them, these orbitals are essentially localized to just a few atoms (always more than 1 making them molecular rather than atomic).
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Comments

  • Curious Wavefunction  On October 3, 2012 at 9:44 am

    That’s why they say that you can never prove a reaction mechanism, only disprove it. This is especially true of organometallics. Popper would be pleased.

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