REACTIONS OF PHENYL-SUBSTITUTED HETEROCYCLIC COMPOUNDS: V. NITRATIONS OF 1,3- AND 1,5-DIPHENYLPYRAZOLES

1964 ◽  
Vol 42 (7) ◽  
pp. 1605-1615 ◽  
Author(s):  
Brian M. Lynch ◽  
Yuic-Yung Hung
Keyword(s):  
Nitric Acid ◽  
Magnetic Resonance ◽  
Acetic Anhydride ◽  
Sulphuric Acid ◽  
Heterocyclic Compounds ◽  
Substituted 1

Dinitration of 1,3- or 1,5-diphenylpyrazole in sulphuric acid yields the corresponding di(p-nitrophenyl) compounds, while nitric acid–acetic anhydride yields the 4-nitro-1-p-nitrophenyl compounds.Mononitration at the 4-position occurs when the diphenylpyrazoles and several other 1-phenylpyrazoles are nitrated at 0° by nitric acid–acetic anhydride.Possible explanations of the dependence of orientation on the nature of the nitrating agent-are discussed.Nuclear magnetic resonance (n.m.r.) spectroscopy was used in demonstrating the structures of many of the nitration products, and a general discussion of the n.m.r. spectra of substituted 1-phenylpyrazoles is given.

Reactions of phenyl-substituted heterocyclic compounds. VII. Reagent-dependent orientation in the nitration of 4-phenylpyrimidine

1967 ◽  
Vol 45 (13) ◽  
pp. 1431-1437 ◽  
Author(s):  
Brian M. Lynch ◽  
Lizzie Poon
Keyword(s):  
Nitric Acid ◽  
Acetic Anhydride ◽  
Nucleophilic Addition ◽  
Heterocyclic Compounds ◽  
Trifluoroacetic Anhydride ◽  
Reaction Products ◽  
Heterocyclic Nitrogen

In the nitration of 4-phenylpyrimidine, the nature of the reaction products is strongly dependent upon the nitrating reagent. Mixed nitric and sulfuric acids yield 4-o- and 4-m-nitrophenylpyrimidines in the ratio 2:3, whereas nitric acid – trifluoroacetic anhydride yields 4-o-, 4-m-, and 4-p-nitrophenylpyrimidines in the ratio 45:29:26, and nitric acid – acetic anhydride yields 2,4-diacetoxy-1,3,5-trinitro-6-phenyl-1,2,3,4-tetrahydropyrimidine.An explanation of these findings involves the possibility of the addition of nitronium ion at the heterocyclic nitrogen, followed in some circumstances by nucleophilic addition.

REACTIONS OF PHENYL-SUBSTITUTED HETEROCYCLIC COMPOUNDS: II. NITRATIONS AND BROMINATIONS OF 1-PHENYLPYRAZOLE DERIVATIVES

1963 ◽  
Vol 41 (6) ◽  
pp. 1540-1547 ◽  
Author(s):  
Misbahul Ain Khan ◽  
Brian M. Lynch ◽  
Yuk-Yung Hung
Keyword(s):  
Nitric Acid ◽  
Acetic Anhydride ◽  
Heterocyclic Compounds ◽  
Electrophilic Substitution ◽  
Chloroform Solution ◽  
Pyrazole Ring ◽  
Conjugate Acid ◽  
Acetyl Nitrate ◽  
Silver Sulphate ◽  
Mixed Acids

Nitrations of 1-phenylpyrazole (I), 1-p-biphenylylpyrazole (II), and 1,5-diphenylpyrazole by "acetyl nitrate" (nitric acid – acetic anhydride) occur selectively in the 4-position of the pyrazole ring, as do brominations of I and II in chloroform solution. These results are in agreement with R. D. Brown's calculations of localization energies for electrophilic substitution in pyrazole.However, nitration of I by mixed acids at 12° yields 1-p-nitrophenylpyrazole, and bromination of I by bromine in concentrated sulphuric acid in the presence of silver sulphate yields 1-p-bromophenylpyrazole.The variations in orientation of substitution can be rationalized if the reacting species of I in strongly acidic solvents is the conjugate acid, in which the pyrazole ring is deactivated by protonation.

POLYVINYL NITRATE

1949 ◽  
Vol 27b (8) ◽  
pp. 705-715
Author(s):  
R. V. V. Nicholls ◽  
S. A. V. Deans
Keyword(s):  
Nitric Acid ◽  
Acetic Anhydride ◽  
Polyvinyl Alcohol ◽  
Nitrogen Content ◽  
Sulphuric Acid ◽  
Fuming Nitric Acid ◽  
Polyvinyl Nitrate

Existing methods of nitration of polyvinyl alcohol involving the use of fuming nitric acid alone, or mixtures of fuming nitric acid and sulphuric acid have been modified to give products improved in nitrogen content, color, and yield. A method involving the use of fuming nitric acid and acetic anhydride has been developed. The explosive characteristics of polyvinyl nitrate of various degrees of polymerization prepared by five different methods are reported.

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