ChemInform Abstract: THERMOLYSIS OF 2‐ACETOXY‐Δ3‐1,3,4‐OXADIAZOLINES. EVIDENCE FOR STEPWISE HOMOLYSIS OF CYCLIC DIAZENES

Yeung, Dominic W. K.; MacAlpine, Gerald A.; Warkentin, John

doi:10.1002/chin.197827087

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“…Warkentin and co-workers (26)(27)(28)(29)(30)(31)(32)(33)(34) have shown that a series of 3 triazolines (12)(13)(14) gives exclusive 3-piece fragmentation, whereas iminooxadiazoline 15 N-P: and oxadiazolinone 16 demonstrate competing in-data for appropriate model compounds to estimate dependent mechanisms for 1,3-dipolar cycloreversion thermodynamic quantities of interest for these and 3-piece fragmentation. In examining these diazenes and their reactions.…”

Section: Thermal Fragmentation Patterns Of 5-memberedmentioning

confidence: 99%

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A relative extrusibility scale and its application to the thermal fragmentation patterns of 5-membered ring diazenes

Paine¹,

Warkentin²

1981

Can. J. Chem.

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Extrusion of a stable molecular fragment (like N2, CO2, SO2, CO, etc.) is a common chemical process. Using thermodynamic additivity concepts, group values, and heat of formation data, a Relative Extrusibility Scale (ΔHex0) has been defined for these fragmentations:[Formula: see text]Twenty-four such extrusions spanning 150 kcal mol−1 have been compiled. Typical values include N2 (−42.0), CO2 (−2.6), HCN (13.8), CO (15.4), H2CO (18.3), C2H4 (32.2), and 1CH2 (109). Among other theoretical and mechanistic applications, this list should be useful when designing synthetic routes involving extrusion reactions.In a particularly effective illustration of the usefulness of the scale, it rationalizes, for the first time, the variety of product types obtained from thermolyses of 14 different kinds of 5-membered ring diazenes. Heat of formation data on most of these compounds do not exist and they contain such sufficiently complicated functional group arrangements that most of the thermodynamic group equivalents are also unknown. This problem can be circumvented by thermodynamic cycles based on the Relative Extrusibility Scale, suitable models, and interfragment resonance corrections. Within an error framework of less than ± 5 kcal mol−1, enthalpy estimates are sufficiently accurate to give heats of reaction capable of predicting which of the potential fragmentation routes actually occur. Formation of a 3-membered ring must be exothermic by at least 30 kcal mol−1 to contribute to the products, but 3-piece fragmentation and 1,3-dipolar cycloreversion will contribute to the observed products when the process is either thermoneutral or exothermic. The unimportance of entropy is also discussed.

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Section: Thermal Fragmentation Patterns Of 5-memberedmentioning

confidence: 99%

“…The heat of formation of dimethyl a-lactone (18) is estimated in eq. [14], leading to a reaction enthalpy of -2 kcal for 3-membered ring formation. The differences between 166 and 16a were set equal to the difference between 15b and 15a (next section).…”

Section: Oxadiazolinone Idamentioning

confidence: 99%

A relative extrusibility scale and its application to the thermal fragmentation patterns of 5-membered ring diazenes

Paine¹,

Warkentin²

1981

Can. J. Chem.

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ChemInform Abstract: THERMOLYSIS OF 2‐ACETOXY‐Δ3‐1,3,4‐OXADIAZOLINES. EVIDENCE FOR STEPWISE HOMOLYSIS OF CYCLIC DIAZENES

Abstract: Die Thermolyse der Titelverbindungen (I) ergibt statt der erwarteten Epoxide vom Typ (V) die Ether (II) als Hauptprodukte.

Cited by 1 publication

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A relative extrusibility scale and its application to the thermal fragmentation patterns of 5-membered ring diazenes

A relative extrusibility scale and its application to the thermal fragmentation patterns of 5-membered ring diazenes

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