Steric Effects in the Nitrosation of Piperidines1

The rates of reaction with nitrous acid of four methylsubstituted piperidines to form the corresponding Nnitrosopiperidines were compared with that of piperidine. The relative rates for piperidine, 2-methyl-, 2,6-dimethyl-, and 2,2,6,6-tetramethyl-piperidine were approximately 100:20:10:1, showing considerable steric hindrance tp nitrosation by the «methyl groups. The rate of formation of nitrosopiperidine from the tertiary amine /V-methylpiperidine was about 10,000 times slower than that from piperi dine.