Anslyn pp. 627 – 703

Great chapter, but why would a nascent organic chemist go into physical organic chemistry?  I’m sure there are I’s to be dotted and T’s to be crossed, but most people going into any branch of science want to find something new and exciting.  Even A&D admit this in the chapter’s last paragraph “it seems unlikely that fundamentally new mechanistic pathways for organic molecules will emerge”.  True enough, but new reactions always will always be found, and you need to know this stuff to figure out what is really going on.  

P. 631 — I don’t think LTMP is actually shown in the ‘Going Deeper’ side bar. 

p. 633 — The explanation of the mostly trans product in 4 tBu cyclohexanone seems fishy as it totally ignores the steric hindrance of the tBu group.   

p. 634 — Nice to have the value in kCal/mole for allylic strain (3 – 4), but it should have been given when first discussed on p. 100.  The value for diaxial strain is also given — I’m sure this was discussed earlier but it isn’t in the index.

p. 639 — The explanation of the common ion effect is confusing. 

p. 647 — When starting to read about a solvent separated ion pair, I wondered how anyone would find independent evidence of it.  The way they did it was clever.  The concept probably has great relevance to membrane biology, as all phospholipids have a negative charge facing the liquid bathing them.  Are ions bound directly to them or separated by solvents?  Chemistry becomes particularly tricky at interfaces — but this is exactly where this sort of thinking is needed.   I see Winstein cited here — this is why Schleyer called him Solvolysis Sol. 

p. 657 — The rapid equilibration of the cyclopentenyl cation even at -139C is fascinating, and something I wouldn’t have predicted.  Maybe chemical bonding is more fluid than I would have supposed. 

p. 661 -> 664 — Fascinating to see the ‘answer’ to the questions about classical and nonclassical norbornyl cations that so exercised Schleyer and many other chemists back in the late 50’s and early 60’s.  Stable ion media and solid state NMR (both unknown at the time) did the trick.  Not finding distinct NMR structures at 5 degrees KELVIN is good enough evidence (for me) that nonclasical norbornyl cations exist.  Also if the barrier to interconversion of 2 norbornyl cations is under .2 kiloCalories/mole, this makes the controversy essentially irrelevant at room temperature and above, where the average thermal energy/molecule is .6 kiloCalories/mole.  Even if two forms actually exist, it’s got to be like keto-enol tautomerism.  A fascinating conclusion to the controversy. 

p. 666 — The dodecaboranes and the carboranes are fascinating.  Lipscomb was starting to work on them when I was in chemistry — most of the attention was paid to the (until then) wierd bonding in B2H6. 

p. 673 —  “Termination usually involves the formation of a tetroxide”  — four oxygens in a row — wow !  Why not 6, 8 or more?  What is the evidence for tetroxides?

p. 681 — Interesting to know that oxime isomers can stably exist as E and Z.  I wouldn’t have thought so. 

p. 684 — Why would Breslow want to functionalize the methyl group (carbon # 18) between the 6 and 5 membered rings of the steroid nucleus?   Because it is functionalized (a CHO group)  in aldosterone, a steroid hormone vitally involved in maintaining blood pressure.  Aldosterone is made by the adrenals, and people deficient in adrenal function have low blood pressure, while those with NO adrenal function at all die of shock when stressed in any way.  Hydrolysis of the oxime shown would produce a C18 aldehyde.

p. 688 — What is sensitized photolysis? Explained on p. 957 but there should be some link to it here.   Also what is a triplet manifold?

 Not that it hasn’t been interesting so far to see where things have gone, but transition metal organic chemistry, photochemistry and quantum mechanical calculations were barely getting started in the early 60s.  The remainder of the book is likely to be quite new and unfamiliar, and we’ll see if I’m able to understand and retain.   Always good to try and learn with a bit of anxiety on board (e.g. am I smart enough to learn this stuff?).  Stay tuned.  

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