Pyrolysis of aromatic azines

Hirsch, Stephen S.

doi:10.1021/jo01283a016

Cited by 10 publications

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“…This was doubtlessly due to the facile decarboxylation which pyrazinecarboxylic acids undergo. Testing of the new polyimide film was conducted with two chief goals in mind: (1) comparison of high-temperature resistance in air with that of a well known, hydrogen-containing polyimide and ( 2 ) demonstrating that the thermal resistance in air was similar to that in nitrogen, which would indicate oxidation resistance. In the first test, samples of PTDA-DATD PI film were compared with specimen films of the polypyromellitimide of oxydianiline.…”

Section: Discussionmentioning

confidence: 99%

Thermostable organic polymers devoid of hydrogen and other pendent groups

Hirsch¹

1969

J. Polym. Sci. A‐1 Polym. Chem.

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SynopsisAromatic hydrogen atoms in thermostable polymers can be surprisingly labile at relatively low temperatures and may participate extensively in degradative reactions. If hydrogen were eliminated from the polymer chain, a number of degradative pathways would be excluded. Replacement of hydrogen with other pendent groups such as fluoride or trifluoromethyl still leaves a potential "handle" to enter into unwanted reactions, therefore, all bonds not required to create the chain were eliminated. The polyimide devoid of hydrogen from pyrazinetetracarboxylic dianhydride and 2,5-diamino-1,3,4-thiadiazole was synthesized. This polymer exhibits extraordinary high temperature oxidation stability. Films of this composition support weight in air up to 592OC, and rupture at this temperature is accompanied by no charring whatever. By comparison, the corresponding polymer from pyromellitic dianhydride, with two hydrogen atoms per repeating unit begins to char at 320°C.

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Section: Discussionmentioning

confidence: 99%

Thermostable organic polymers devoid of hydrogen and other pendent groups

Hirsch¹

1969

J. Polym. Sci. A‐1 Polym. Chem.

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“…The crystals which formed were filtered off, washed with cyclohexane and dried to give a brown solid (2.04 g), m.p. 150 "C (from ethanol); 6, 8.82 (1 H, s), 8.19 (1 H, d), 5.88 (1 H, d), 3.11 (6 H, s), and 3.08 (6 H, s); mjz 185 ( M + , 96%), 152 (17), 130 (loo), 114 (30), 97 (30), and 82 (30). The 'H n.m.r.…”

Section: -Dimethylamino-1-phenyl-1-azaprop-2-ene-1-thione (12)-mentioning

confidence: 99%

Thermolysis of polyazapentadienes. Part 11. Concerted and free radical mechanisms in 2-aza enone and 2-aza enthione pyrolyses: crystal and molecular structures of 3-dimethylamino-1-p-tolyl-2-azaprop-2-en-1-one and 3-dimethylamino-1-phenyl-2-azaprop-2-ene-1-thione

Blake¹,

McNab²,

Murray³

1989

J. Chem. Soc., Perkin Trans. 1

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Flash vacuum pyrolysis of the dimethylamino-azapropenones (7)-( 9) and -azapropenethione (1 2) gives nitriles and amides (or thioamide) in yields of ca. 30% by an electrocyclisation-ring cleavage mechanism. This is a minor pathway for the triarylazapropenones ( 14) and (15) for which homolytic cleavage of the C-N bond gives rise to the major products. The X-ray crystal structures of ( 10) and (I 2)show that the conjugated systems are almost planar in the s-Z conformation, as required for the electrocyclic ring closure.The work described in the previous paper explores the thermal cleavage of HCN from the central atoms of an azoalkene unit (1). The terminal nitrogen atom is apparently not necessary for this behaviour, since there is considerable evidence that 2-aza dienes (2) can decompose by a similar mechanism,2 and that other terminal hetero-atoms can also become involved e.g. (3).3 However, alternative free-radical cleavage may be observed, e.g. (4).' An extension of these ideas to 2-aza enones ( 5 ) and 2-aza enethiones (6) is now described, in which the interpretation of the pyrolysis results is reinforced by X-ray crystallographic studies of typical precursors.

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Enazine chemistry II. The mechanism of formation of 1‐(cis‐3‐phenylpropenyl)‐5‐phenylpyrazole from the pyrolysis of cinnamaldehyde azine

Stern

Krause

1968

Journal of Heterocyclic Chem

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The mechanism of pyrazole formation from the thermolysis of α,β‐unsaturated azines has been examined by both kinetic and non‐kinetic methods. The reaction exhibits a large negative entropy of activation, a large primary isotope effect and a positive slope in a Hammett study on cinnamaldehyde derivatives. The reaction was shown to be cleanly intramolecular and was also unaffected by radical traps. A mechanism involving intramolecular 1‐5 abstraction of a proton is presented, which accounts for all of the experimental data.

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Pyrolysis of aromatic azines

Cited by 10 publications

References 0 publications

Thermostable organic polymers devoid of hydrogen and other pendent groups

Thermostable organic polymers devoid of hydrogen and other pendent groups

Thermolysis of polyazapentadienes. Part 11. Concerted and free radical mechanisms in 2-aza enone and 2-aza enthione pyrolyses: crystal and molecular structures of 3-dimethylamino-1-p-tolyl-2-azaprop-2-en-1-one and 3-dimethylamino-1-phenyl-2-azaprop-2-ene-1-thione

Enazine chemistry II. The mechanism of formation of 1‐(cis‐3‐phenylpropenyl)‐5‐phenylpyrazole from the pyrolysis of cinnamaldehyde azine

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