Basicity comparisons TBR possible mistake

[ryblake]

Example 7.9 in Organic Chemistry Chapter 7: Nitrogen compounds. I bought my books in December 2013 if that gives an indication as to which version I have.

How can it be explained that the Compound AWL8386 is more basic than Compound KMF8889?

A. Aromaticity reduces the availability of the electron pair for donation in Compound AWL8386.
B. The inductive effect is greater in Compound KMF8889.
C. The steric hindrance is greater in Compound AWL8386.
D. The nitrogen in Compound KMF8889 lacks hybridization.

Solution
The lone pair on nitrogen in Compound KMF8889 is tied up in the aromatic ring of the pyrrole. This makes it less available for sharing with a protic hydrogen, and thus makes the compound less basic. This makes choice A the best answer.

I'm pretty positive they just put the wrong compound name into choice A, but just wanted some back up from someone else.

Thanks,

Ryan

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[Chrisz]

The answer is indeed A. The lone pair of nitrogen of KMF8889 is in the p-orbital instead of sp3 so that the lone pair can have conjugation with the pi electrons in the double bond and and therefore make it aromatic. If the lone pair is protonated, the aromaticity will be lost. The aromatic property makes the lone pair very stable so it is less likely to be basic. So AWL8386 is more basic since it does not have aromaticity

 

[Chrisz]

Sorry for skimming too fast earlier. Yeah they misplaced name in A

 

[ryblake]

Thank you!

 

[Lunasly]

Yes, this error is still present in the 2014 edition of TBR. Really wish I bought earlier versions of the book now as there doesn't seem to be much change.

 

[JMMTB]

Ya I've come upon quite a few mistakes in TBR ochem. Especially in the answer key. At the end of the passages the box with the answers doesn't always match the detailed explanations answers. e.g. Section 2: 37 (letter matches but description says completely different number), 52 (letters don't match) and more...