N-H from primary amides

N-H from primary amides, secondary amides both alkyl and aryl group associations... 

N-H from primary amides (R-C=0-NH2) N-H (2v) symmetric from primary amide (R-C=0-NH2) N-H from primary amides... 

Polyamide 11 N-H from primary amides N-H from primary amides N-H from protein Polyamide 11... 

N—H Bending Vibrations (Amide II Band) All primary amides show a sharp absorption band in dilute solution (amide II band) resulting from N—H, bending at a somewhat lower frequency than the C=0 band. This band has an intensity of one-half to one-third of the C=0 absorption band. In mulls and pellets the band occurs near 1655-1620 cm-1 and is usually under the envelope of the amide I band. In dilute solutions, the band appears at lower frequency,... 

The carbonyl stretching of amides occurs at 1630-1680 cm , a lower series of wave-numbers than for other carbonyl compounds. Primary and secondary amides show N—H stretching in the region from 3200 to 3400 cm primary amides (RCONHg) show two N—H absorptions, whereas secondary amides (RCONHR) show only a single N—H absorption. Tertiary amides, of course, do not show N—H stretching absorptions. See the three spectra in Figure 11.13. 

N-H combination band from primary amides N-H [vN-H asymmetric and Amide N-H combination bmd 1 3... 

Another alternative for preparing a primary amine from an alkyl halide is the Gabriel amine synthesis, which uses a phthalimide alkylation. An imide (—CONHCO—) is similar to a /3-keto ester in that the acidic N-H hydrogen is flanked by two carbonyl groups. Thus, imides are deprotonated by such bases as KOH, and the resultant anions are readily alkylated in a reaction similar to the acetoacetic ester synthesis (Section 22.7). Basic hydrolysis of the N-alkylated imide then yields a primary amine product. The imide hydrolysis step is analogous to the hydrolysis of an amide (Section 21.7). 

Model primary amides (8.168, R = Me or Ph, X = H, Cl, or N02) were used to investigate the mechanism of hydrolysis of their AA (acyloxy )melh-yl] derivatives [217], These compounds were hydrolyzed very rapidly, with tm values at pH 7.4 and 37° of ca. 1 min. This is much faster than predicted from structure-reactivity relationships, and led to the suggestion of an elimination-addition mechanism involving a reactive N-acy I inline intermediate (acyl-N=CH2). In contrast, N- [(acyloxy)methy 1] derivatives of imides... 

The N-H protons of primary and secondary amides are slow to exchange and require heating or base catalysis and this is one way an amide functional group can be distinguished from other functional groups. 

Other Vibration Bands The C—N stretching band of primary amides occurs near 1400 cm-1. A broad, medium band in the 800-666 cm-1 region in the spectra of primary and secondary amides results from out-of-plane N—H wagging. 

Formation of an amide is also indicated in the reaction of PCTFE with Cr(CO)6 and the primary amine, benzylamine. The infrared absorption spectrum shows an N-H stretch centered at 3400 cm, aromatic C-H stretches at 3063 and 3030 cm1, aliphatic C-H stretches at 2933 and 2876 cm1, a broad amide I/amide II band ranging from 1680-1580 cm1, and a C-N stretch at 1454 cm1. The C-Cl stretch at 970 cm1 also shows a significant decrease in... 

Sulfonylation of amines can be a useful way of differentiating (chemically) between primary, secondary, and tertiary amines by what is known as the Hinsberg test. Primary and secondary amines both react with a sulfonyl chloride, but only the sulfonamide from the primary amines has an N—H hydrogen. The sulfonyl group makes this hydrogen relatively acidic and the sulfonamide therefore dissolves readily in sodium hydroxide solutions. The secondary amine does not give a base-soluble amide, whereas the tertiary amine gives no sulfonamide ... 

We will see that this technique can be used to demonstrate the importance of the principle of stereoelectronic control in tetrahedral intermediates derived from amides. Primary, secondary, and tertiary amides as well as N — H and N-alkyllactams will be examined. 

Amides. All amides are characterised by a strong carbonyl absorption band, referred to as the amide I band. Primary and secondary amides additionally show bands arising from N—H stretching and bending vibrations. The N—H... 

In dilute solution primary amides show two sharp bands resulting from the asymmetric and symmetric N—H stretching vibrations near 3520 cm-1 and 3400 cm-1 (the normal N—H region). In solid samples these appear near 3350cm-1 and 3180cm-1. In dilute solution secondary amides show only one band near 3460-3420 cm-1 on low-resolution instruments. However, under conditions of high resolution the band can frequently be split into two components which have been assigned to the cis and trans rotational isomers. 

Bands resulting from the primary and secondary N—H bending vibrations appear near 1650 cm-1 and 1550 cm-1 respectively in the solid phase, and the large difference in these amide II bands enables primary and secondary amides to be distinguished. The 1550 cm -1 band is not a simple N—H bending mode, but is believed to result from coupling of this deformation with a C—N stretching vibration. 

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