The New Clayden pp. 562 – 613

p. 564 — “The black proton removed in the third lithiation is more acidic because it is next to an aromatic ring — true enough but there are 4  more such protons in the molecule.   Why aren’t they attacked? 

p. 566 — It’s hard to figure out just how close SO3H is to the hydrogens in naphthalene without knowing naphthalene carbon carbon bond lengths (which I can’t seem to find).  Probably they don’t change much, and all C-H bonds should be the same. 

p. 571 — “to make radicals we need weak symmetric bonds such as O-O, Br-Br, or I-I”.  Why not give the actual bond strengths which are (respectively) 33, 46 and 36 kiloCalories/Mole.  In contrast the C-C bond is 83, the C-H is 96 – 105, the C-0 bond is 84, and the C-N bond is 69 kiloCalories/Mole.  The book seems to be relentlessly nonQuantitative (probably an editorial decision).   Then, a bit later it is noted that the phenylcarboxy radical will homolytically cleave H-Br because a very strong OH bond will be formed — but no number is given — here it is — 110 – 119 kiloCalories/Mole.    I find the numbers helpful, perhaps beginning students wouldn’t. 

p. 572 “As bromine is brown, it absorbs most wavelengths of visible light” — exactly backwards  — the energy levels of Br2 don’t care what color it is, the difference between them is in the energy range of visible light, which is why bromine is colored.  If it absorbed all light in the visible region it would be black. 

p. 574 — Frontier orbitals — the term is used, but as far as I can tell it was never defined when HOMO and LUMO (which is what they are) were introduced on p. 111.

p. 576 — line 2  “regioslectivity’

p. 581 — “As a C=0 pi bond is stronger than a C=C pi bond”  — this ignores the fact that a C – O bond is also  slightly stronger than a C – C bond.  Thermodynamics cares only about the total energy of the final products, and the C = 0 bond takes 172 kiloCalories/mole to dissociate it while the C = C takes 143, a difference of 29 kiloCalories mole.  Since at 298 K (where RT = .6) every 1.36 kiloCalories/mole changes the equilibrium constant by a factor of 10.   The equilibrium constant should be 10^29/1.36 = 10^21, other things being equal (which they aren’t quite when other bond strengths are factored in). 

p. 590 — Halfway through the book — great fun, well written, bravo.  A lot of the irritants of the previous edition have been removed (notably back references to chapters, rather than specific pages).  In a future edition I think there should be actual values for bond lengths, and bond strengths rather than saying stronger or weaker, longer or shorter. 

p.595 — Alkylation of beta-carbonyls — ho hum. Not so !  The field is alive and well with brand new stuff (5 July ’12) coming out.  See Nature vol. 487 pp. 47 – 48, 86 – 89 ’12 — Leighton uses chiral allylsilanes to react with aldehydes and beta diketones to produce beta hydroxy, beta-allyl ketones which are optically active (because the allyl silane is).  The chiral allylsilane is first tethered to the enol adjacent to an aryl group, and then the fun begins.   The reaction doesn’t discriminate between beta diketones with two different alkyl groups.  Hard core organic chemistry.    Starting from a general chemistry background and reading Clayden to p. 595 tells you just about all you need to know to understand hot stuff in the current literature — not bad ! ! !

p. 599 — Hydride is stated to be ‘small’  — clearly bigger than a proton — it should be the smallest anion around (aside from the electron).  But it isn’t — according to Wikipedia — its ionic radius is 1.46 Angstroms, while that of the fluoride anion is 1.33 (more positive charge pulling the electrons toward the nucleus). 

p. 607 — In the second structural reaction sequence from the body, the tBuOK is on the wrong arrow in the leftmost equilibrium shown.

p. 608 –Line 8 —  “neat” is a chemical term of art, which should be defined. Ditto for work-up (line 13).

p. 608 — Sidebar — there’s nothing about Lewis acids on p. 466.

p. 612 — Just saying ‘dopaminergic antagonist’ is likely to leave chemists (and even premeds) mystified.  You might mention that dopamine antagonists were the first useful drugs we had against schizophrenia and other psychoses.  They are still in use today, although clearly they aren’t perfect or curative.
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