The middle ultraviolet absorption of some pyrazoles derived from β-dicarbonyl compounds was written by Dayton, Peter G.. And the article was included in Compt. rend. in 1953.Product Details of 934-48-5 This article mentions the following:
The bathochromic effect of substituents on the absorption of pyrazole increases as follows: pyrazole < alkylpyrazole < pyrazolecarboxylic acid < phenylpyrazole < phenylpyrazolecarboxylic acid. Absorption spectrum curves between 3000-2142 A. are given for pyrazole and its following derivatives (substituents given): 3(5)-Me (I); 1,3,5-tri-Me; 1-Ph, 3(5)-tert-Bu, m. 75-6°, b760 268°, b18 152°; 1-Ph,3(5)-Me, 5(3)-tert-Bu, m. 85°, b758 272°, b14 153°; 1-Ph, 3,5-di-Me (II); 3(5)-Ph; 3,5-di-Me, 1-H2NCO (III); 3,5-di-Me, 4-EtO2C; 3(5)-HO2C; 1-Ph, 3,5-di-Me, 4-EtO2C; 3(5)-Ph, 5(3)-EtO2C. The 3,5-di-Me, 3(5)-tert-Bu, m. 53-5°, b760 214°, b15 115°, and 3(5)-Me, 5(3)-tert-Bu, m. 169-71°, b760 225°, derivatives all show the same absorption as I; the 1-Ph, 3,4,5-tri-Me derivative the same as II, and the 5(3)-tert-Bu, 1-H2NCO, m. 93°, and 3(5)-Me, 5(3)-tert-Bu, 1-H2NCO, m. 113-14°, the same as III. In the experiment, the researchers used many compounds, for example, 3,5-Dimethyl-1H-pyrazole-1-carboxamide (cas: 934-48-5Product Details of 934-48-5).
3,5-Dimethyl-1H-pyrazole-1-carboxamide (cas: 934-48-5) belongs to pyrazole derivatives. Pyrazole has two ring nitrogen atoms in which N1 is pyrrolic and N2 is pyridine-like. The N1 nitrogen is not reactive but is deprotonated in the presence of a base-forming anion. Protonation of pyrazole in strong acid leads to pyrazolium cations, which undergo electrophilic substitution preferentially at C3 rather than C4. The pyrazole anion is not reactive toward nucleophiles but is mostly reactive to electrophiles.Product Details of 934-48-5
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics