Clayden pp. 1000 – 1099

 


 

 

 

p. 1004 “the electron source and sink are separated by one atom in stead of being adjacent”   This is confusingly written  — being adjacent means the source and sink are bonded to adjacent atoms (which are bonded to each other), being separated by one atom really means the atoms the source and sink are bonded to are separated by another atom.  There ought to be a better way to express this. 


 


p. 1009 — The rightmost compound in the second from the bottom row is missing a carbonyl group next to the 4 membered ring. 

p. 1008 — When looking at the Eschenmoser fragmentation, I get the same feeling as I get while trying to learn the Brahms Paganini variations?  How in the world did they ever think of it?   You say he ‘discovered’ it.  Was it serendipity?  What was he trying to do with the Tosyl-hydrazine?

p. 1015 — (bottom) isn’t it rather an oxyallyl zwitterion rather than an oxyallyl cation? 

p. 1018    Think the answer to the first half #13 is incorrect.  A hydrogen appears out of nowhere in the middle structure of the answer.  

Chapter 39:  Something about this chapter just doesn’t flow as well as the others.  I can’t put my finger on it.  Not trying to insult the author.

p. 1020 – 1021 — In the table on p. 1020 deltaG is given for the reaction X-Y –> X. + Y.   Exactly the same numbers are given for deltaG* (the activation energy) on p. 1021 for Cl-Cl, Br-Br, I-I.  I don’t think deltaG ever is the same as deltaG*  — what’s going on? 

p. 1024 — “Unpaired electrons are desperate”    when did electrons acquire consciousness?  “Bachelor electrons”  — leave it to the French.  C’mon now.  Forgetting the language, you should here provide some sort of explanation (assuming one exists) for their desperation. 

p. 1025 — Why no coupling constants for ESR?

p. 1027 —  The caption in the box outlined in red  on the bottom molecular orbital diagram is incorrect — it should be radical stabilized by electron withdrawing group. 

p. 1040 — When first discussing Bu3SnH it would be good to note that the electronegativity of Sn is 1.96 while that of H is 2.2 explaining why it is called a tin hydride. A mention of why electronegativity decreases as atomic number increases in any one column wouldn’t be a bad idea at this point.

p. 1041 — “Peroxides, on the other hand generate RO. radicals.  These are highly reactive” — you bet they are, and the body has all sorts of defenses against them.  Such radicals are produced by ionizing radiation, and even by the normal activity of mitochondria in the course of generating ATP.  You might put in something in the next edition to this effect. You might point back to p. 1024 where you discuss vitamin E at this point.

p. 1051 Problem #1 (answer) “If the esters can form enolates, the addition of Me3SiCl protects against the problem by removing the EtO-  by-product.  EtO- should be MeO-.

p. 1052 — DMAP wasn’t defined as dimethylamino pyridine until p. 1153.  One of the few times a term was used in the book prior to its definition. 

p. 1054 — N-methyl N-nitroso urea is a wierd looking molecule.  How is it made?  The N-ethyl variant is used as a mutagen in molecular biological work.  The same goes for a lot of the weird reagents (AIBN, etc. etc) found in the book.  Clearly, they don’t arise by magic.   

p. 1054 — “toxic and highly explosive gas”  — I never had any mishaps with diazomethane in grad school when I (skittishly) worked with it, despite my lousy lab technique.  It was (and apparently still is) scary stuff. 

p. 1055 — “the potential for serious explosions is too great” — for photolysis.  This is exactly what I was attempting to do (generate a carbene from R – CO – CH – N2). 

p. 1057 — The mechanism of diazo exchance with tosyl azide could use some expanding. 

p. 1058 — Azirine is nowhere defined in the book (amazing that this is one of the few, and perhaps the first, example I could find).

p. 1062  — “Most type of carbenes are more stable as triplets because the energy to be gained by bringing the electron in the p orbtal down into the sp2 orbital is insufficient to overcome the repulsion that exists between two electrons in a single orbital.”   This is fairly stunning.  This implies that the energy level of an orbital isn’t constant but rather depends on whether one or two electrons is in it.  This should be noted and/or elaborated in the next edition.  

p. 1062 — Apparently the electronegativity of Cl (3.16) doesn’t matter when it comes to electron donation to an adjacent carbene– nor does oxygen (3.44).

p. 1062 — The labels on the orbital energy diagram don’t make sense as they appear to be talking about both a singlet carbene and a triplet carbone.

p. 1064 — You might say that the triplet intermediate in the reaction of the triplet carbene can’t form a bond as a direct consequence of the Pauli exclusion principle.

p. 1064 — “Spin-flipping, which can only occur through collision with another molecule (of solvent say) is relatively slow on the time scale of molecular rotations”  — true, but how about some numbers?  Surely these are known.

As biochemistry gets down to the single molecule level which we can now measure, it would be very nice to know how fast ions move at room temperature, how quickly molecules tumble and move, what rotations rates around bonds actually are, etc. etc.  

p. 1071 — With respect to the synthesis alpha-cuprenone, the starting material must have 3 adjacent carbonyls.  How is such a thing actually made? 

p. 1068 — “As you might imagine, carbenes like this (E2O2C-CH=N=N) with electron withdrawing carbonyl groups are even more powerful electrophils than carbenes like :CCl2 “  — Cl with an electronegativity of 3.16 isn’t electron withdrawing?  Probably the reason for this statement is the donation of unpaired electrons to the carbene — noted on p. 1062

p. 1070 — Any ideas why the carbene in the reaction shown in the bottom row forms a 5 membered ring rather than a 6 membered ring?  The very next reaction (top of p. 1071) has a nearly identical alpha keto-carbene forming a 6 membered ring.

p. 1074 — Hilariously, metathesis does not appear in your index as the lead word, but under alkene metathesis (and olefin metathesis) .  I tried to look it up long before I got to this page and wondered why it wasn’t in such a comprehensive textbook.  Definitely to be corrected in the next edition.  Also I think the discussion of metathesis is incredibly skimpy — hopefully it will be expanded in the new edition.  

p. 1076 — (problem #3) — Cu/Ag should be Zn/Ag (as it is in the answer book)

p. 1077 — (problem #8, answer)  I got how to make the cyclopropene, but I felt like I was cheating to use Me3Si -C (triple) C-SiMe3.  How in the world would you make this ? 

p. 1077 — (problem #13) DME is nowhere to be found in the index

p. 1090 — Ah, the Hammett relationship.  Back in the day, it was initially proposed as a way to predict the way benzene substituents would react.  Hordes of graduate students (whose uncreative professors couldn’t think of anything better for them to do) were set to measuring sigman and rho for all sorts of functional groups and reactions.  This seemed to turn into finding explanations for deviations of sigma and rho values from various theoretical constructs rather than a predictive tool.  As I read on through the chapter, hopefully I’ll find that sigma and rho were used for something better.

p. 1093 — Gradient (this appears to be an English usage).  US readers would be more likely to understand gradient as the slope of the line.  Also mathematically, gradient is the way you turn a scalar field (like the temperature at any point in space) into a vector field which points in the direction of the greatest rate of increase of temperature (at each point in space). 

p. 1093 — Another way to look at the positive rho value is that electron withdrawal makes the carbonyl group of the ester more attackable by a nucleophile. 

p. 1097 — An impressive use of the Hammett relationship.  To get the rho values how many points (on average) should  go into the plot, how many actually do?  It seems like a huge amount of drudgery for some hapless grad student.  

p. 1098 — Nonlinear Hammett plots — very elegant. I don’t recall anything like this being done in the early 60s. 

 

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