Bonds carbon-nitrogen single bond

Catalyt c hydrogenation (palladium or Raney nickel catalyst) surprisingly results in reduction of the carbon-nitrogen single bond rather than the double bond.4,12,40 The imines, or possibly enamines, are usually not isolated and their existence has only been inferred in most instances. Harvey and Ratts have shown that this reaction with azirine (165) does not proceed first to the aziridine which is then reduced to 166, since aziridine (167) is inert to hydrogen and palladium on carbon.40... 

Carbon-nitrogen single bonds are freely rotating however, amide carbon-nitrogen bonds are much more rigid. Why is this true What effect does this property of amide bonds have on the shapes that proteins can assume ... 

Ring Closure to Form Carbon-Nitrogen Single Bonds. 548... 

D. RING CLOSURE TO FORM CARBON-NITROGEN SINGLE BONDS... 

The Eigen model requires two different hydrogen-bonded intermediates eorresponding to the two alkene produets that are formed. Eaeh intermediate leads to a different transition state, structures 2 and 3 drawn in Scheme 2. The former, 2, leads ultimately to 1-methylcyclopentene as the final product. This transition state has no overall molecular symmetry, but retains the methyl rotor as well as free rotation about the carbon-nitrogen single bond for a net symmetry number a = 9. Because transition state 2 is chiral, the reaction path degeneracy is equal to (18/ ) = 4. 

Enamines have a carbon-nitrogen single bond with an adjacent carbon-carbon double bond. 

FIGURE 18.18 The structures of some simple acyl compounds. Notice how the carbon-oxygen and carbon-nitrogen single bonds are shortened by the double-bond character that results from the resonance shown in Figure 18.17. 

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