Rate constants for the reactions t-C sub 4 H sub 9 + DX yields i-C sub 4 H sub 9 D + X (X = Br, I), 295 < T(K) < 384: Heat of formation of the tert-butyl radical
- SRI International, Menlo Park, CA (USA)
Absolute values for the rate constants of the metathesis reactions of DX (X = Br, I) with tert-butyl, generated by 351-nm photolysis of 2,2{prime}-azoisobutane, were determined in a low-pressure Knudsen cell reactor using the VLP{Phi} (very low pressure photolysis) technique. For X = Br, the values are 10{sup {minus}8}k (M{sup {minus}1} s{sup {minus}1}) = 0.9 and 2.3, and for X = I the values are 2.1 and 3.1 at 295 and 384 K. The latter are in good agreement with earlier measurements from this laboratory. The former values are lower by a factor of 50 compared to those recently reported at 295 K and fail to show the negative activation energy found in that work. Correcting by {radical}2 for the primary isotope effect and combining with the rate constants for the reverse reactions lead to {Delta}H{sub f}{degree} {sub 298}(tert-butyl) (kcal mol{sup {minus}1}) = 9.2 {plus minus}0.5 in both cases. First-order heterogeneous loss of tert-butyl radicals on the Teflon-coated surface employed is small (< 2 s{sup {minus}}1). 17 refs., 9 figs., 3 tabs.
- DOE Contract Number:
- FG03-86ER13571
- OSTI ID:
- 5050569
- Journal Information:
- Journal of the American Chemical Society; (USA), Vol. 111:3; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
Similar Records
Kinetics and thermochemistry of R + HBr {r_reversible} RH + Br reactions: Determinations of the heat of formation of C{sub 2}H{sub 5}, i-C{sub 3}H{sub 7}, sec-C{sub 4}H{sub 9}, and t-C{sub 4}H{sub 9}
Kinetics and thermochemistry of the reactions of alkyl radicals (CH sub 3 , C sub 2 H sub 5 , i-C sub 3 H sub 7 , s-C sub 4 H sub 9 , and t-C sub 4 H sub 9 ) with HI: A reconciliation of the alkyl radical heats of formation
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BUTANE
CHEMICAL REACTIONS
BUTYL RADICALS
FORMATION HEAT
DEUTERIUM COMPOUNDS
HALIDES
EXPERIMENTAL DATA
TEMPERATURE EFFECTS
ALKANES
ALKYL RADICALS
DATA
ENTHALPY
HALOGEN COMPOUNDS
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
RADICALS
REACTION HEAT
THERMODYNAMIC PROPERTIES
400201* - Chemical & Physicochemical Properties
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation