ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The rate of decomposition of tert-amyl nitrite (t-AmONO) has been studied in the absence (120°-155°C) and presence (160°-190°C) of nitric oxide. In the absence of nitric oxide for low concentrations of tert-amyl nitrite (∼10-4M) and small extents of reaction (∼1%), the first-order homogeneous rates of acetone formation are a direct measure of reaction (1) since k3a ≫ k2(NO): The rate of acetone formation is unaffected by the addition of large amounts of carbon tetrafluoride or isobutane (∼1 atm) but is completely suppressed by large amounts of nitric oxide (1 atm 120°-155°C).The rate of reaction (1) is given by k1 = 1016.3±0.1 10-40.3±0.1/θ sec-1. Since (E1 + RT) and ΔH°1 are identical, both may be equated with D(t-AmO - NO) = 40.9 ± 0.1 kcal/mol and E2 = 0 ± 0.1 kcal/mol. The thermochemistry leads to the result that ΔH°f (t-AmO) = -26.6 ± 1 kcal/mol. From ΔS°1 and A1, k2 is calculated to be 1010.5±0.2 M-1·sec-1.Although the addition of nitric oxide completely suppresses acetone formation at lower temperatures, it reappears at higher temperatures. This is a result of reaction (3a) now competing with reaction (2), thus allowing k3a to be determined. The rate constant for reaction (3a) is given by k3a = 1014.7 ± 0.2 10-14.3 ± 1/θ sec-1. There are two possible routes for the decomposition of the tert-amyloxyl radical: The dominating process is (3a). From the result at 160°C that k3a/k3b = 80, we arrive at the result k3b = 1015.0-18.7/θ sec-1.In addition to the products accounted for by the radical split (1), methyl-2-but-1-ene and methyl-2-but-2-ene are produced as a result of the six-centre elimination of nitrous acid (5): The ratio k5a/k5b was 0.35. Unlike tert-butyl where the rates of the two paths were comparable [(l) and (5)], here the total rate of the elimination process was only 0.5% that of the radical split (1). The reason for this is not clear.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550100904
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