CONVERSION OF CIS TO TRANS STEREOCHEMISTRY IN THE SYNTHESIS OF PIPERCYCLOBUTANAMIDE
H-NMR

Protip: Mouseover rows in the table to see corresponding H on molecule 18 to the right. Two separate sets of mouseovers were added for optimal viewing on all devices.

 

EXPLANATION

HYDROGEN

SHIFT & MULTIPLICITY

Hydrogen A has two vicinal hydrogen neighbors on the cyclobutane ring; the doublet of doublet ostensibly overlaps to appear as a triplet. Coupling constant of 9.7 Hz shared by Hydrogen D.

A

3.15 (triplet)

Hydrogens A and B can be interchanged in terms of chemical shift. Both have two vicinal hydrogen neighbors on the cyclobutane ring. Overlap of doublet of doublet appears as a triplet.

B

3.18 (triplet)

Hydrogen C has one vicinal hydrogen neighbor on the cyclobutane ring and another geminal neighbor on the same carbon (diastereotopic hydrogens). The high chemical shift results from its proximity to the carboxylic acid.
C 3.59 (dd)
Hydrogen D has two vicinal hydrogen neighbors on the cyclobutane ring; the doublet of doublet ostensibly overlaps to appear as a triplet. Higher chemical shift than A/B due to proximity to carbonyl group.
D 4.03 (triplet)
Hydrogen E is has too low a chemical shift to be in the aromatic range, and has one geminal hydrogen neighbor on the same carbon (diastereotopic hydrogens) to produce the doublet.
E 5.93 (doublet)
This hydrogen has two distinct vicinal neighbors: one trans on the double bond, producing the high coupling constant of 15.8 Hz, and another on the cyclobutane ring producing the medium coupling constant of 7.3 Hz.
F 6.27 (dd)
This hydrogen has one vicinal neighbor trans on the double bond, which produces a doublet with a high coupling constant of 15.8 Hz. Same coupling constant as F indicates G is on the same double bond.
G 6.63 (doublet)
This hydrogen is aromatic and has two distinct vicinal hydrogen neighbors, producing the doublet of doublets (7-8 ppm aromatic range).
H 7.42 (dd)
This hydrogen is in the aromatic range and has only one vicinal hydrogen neighbor, producing the doublet (7-8 ppm aromatic range).
I 8.17 (doublet)
This hydrogen has two distinct vicinal neighbors and is in the aromatic range. It has a higher shift than hydrogen I because of its proximity to the electronegative nitrogen atom.
8.80 (doublet)
J
The highest chemical shift along with the singlet multiplicity unequivocally associate this peak with hydrogen K of the carboxylic acid.
K
9.98 (singlet)

 

Protip: Mouseover any labeled hydrogen on molecule 18 to see the corresponding peak on the proton-coupled H-NMR spectrum.

Poor resolution due to low quality spectrum in the supplemental information.

 

University of Michigan Chem 215/216 HH Winter 2014. Nicholas Carducci's Structured Study Group. HTML Project of Callie Chappell, James Lawniczak, Aiman Faruqi, and Ryan Gentil