We report on the syntheses of some p-aminophenones with different lengths in their alkyl chains. In the mass spectra, beginning with p-amino-n-butyrophenone, the m/e 135 ion forms and its intensity increases sharply with alkyl chain length. The lengthening of the alkyl chain increases the intensity of the IR CH stretching absorption in the region of 3000-2800 cm−1 but decreases the complexity in the absorption region from 3.00 ppm to about 0.80 ppm in the PMR spectra.
Huo Ping Pan and Iwao Okuno, "Alkyl Chain Length and the Spectral Characteristics of p-Aminophenones," Appl. Spectrosc. 39, 339-342 (1985)