Doublet primary amines

FIGURE 2.29. 2-Methyl-l,5-pentanediamine. N—H stretch, hydrogen-bonded, primary amine coupled doublet asymmetric, 3368 cm-1. Symmetric, 3291 cm. (Shoulder at about 3200 cm-1, Fermi resonance band with overtone of band at 1601 cm-1. Aliphatic C—H stretch, 2928,2859 cm-1. N—H bend (scissoring) 1601 cm-1. SsCH2 (scissoring), 1470 cm-1. C—N stretch, 1069 cm-1. N—H wag (neat sample), —900-700 cm-1. 

The IR spectrum shows that B is a primary amine, and the H NMR spectrum shows a 9-proton singlet, a one-proton quartet, and a 3-proton doublet. An absorption due to the amine protons is not visible. 

N—H stretching 100 cm doublet for primary amines singlet for secondary amines absent for tertiary amines... 

There are three spectra shown in this problem along with three structures of aromatic primary amines. Assign each spectrum to the appropriate structure. You should calculate the approximate chemical shifts (Appendix 6) and use these values along with the appearance and position of the peaks (singlet and doublets) to assign the correct structure. 

Although the N-H stretching is located between 3500 and 3300 cm-i, primary amines show a doublet (reflecting the symmetric and antisymmetric stretching modes) while the secondary amines show one single band. 

In Figure 4.8, there is a doublet with peaks at 3380 and 3300 cm characteristic of a primary amine. There is also a series of overlapped bands below 3000 cm ... 

N—H stretch. Both aliphatic and aromatic primary amines show two absorptions (doublet due to symmetric and asymmetric stretches) in the region 3500-3300 cm. Secondary amines show a single absorption in this region. Tertiary amines have no N—H bonds. 

As shown in Figure 8.1, primary and secondary amines are distinctly different in the first overtone region near 6600 cm. Primary amines have a doublet, and secondary a single peak. Tertiary amines have no peak as they have no N-H functionality and are not shown in the figure. The asymmetric and symmetric NH-stretching peaks occur at 6553 and 6730 cm (1625 and 1486 nm), respectively, in butyl amine in carbon tetrachloride. The first overtone of secondary amines has only one band near 6530 cm (1530 nm). 

O-H stretch 3300-2500 broad Amines, primary -NH2 Amino acids Esters N-H stretch 3500-3400 doublet, weak NH3 stretch 3100-2600 strong C=0 stretch 1750-1735... 

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