The kinetics of the thermal decomposition of diallylamine to propylene and prop-2-enaldimine have been studied in the gas phase in presence of an excess of methylamine over the temperature range of 532.7 to 615.6"K, using a static reaction system. Methylamine reacted with the unstable primary product prop-2-enaldimine, forming the thermally stable N-methyl prop-2-enaldimine.First-order rate constants, based on the internal standard technique, fit the Arrhenius relationship log kfs-1) = (1 1.04 f 0.13) -(37.1 1 f 0.33 kcal/mole)/2.303 RT. They were independent on the initial total pressure (46-340 torr), the initial pressure of diallylamine (9.2-65 torr), or methylamine as well as the conversion attained. Despite an apparent surface sensitivity, the reaction is essentially homogeneous in nature as demonstrated by experiments carried out in a packed reaction vessel. The observed activation parameters for the title reaction together with those observed earlier for triallylamine and allylcyclohexylamine are consistent with the proposed concerted reaction mechanism involving a cyclic 6-center transition state. The observed substituent effects suggest a nonsynchronous mode of bond breaking and bond formation. Jn troductionT h e thermal decomposition of diallylamine has been investigated as part of a series of studies on the thermochemical kinetics of N-substituted N-allylamines in a n attempt to obtain more information about the effect of substituents and heteroatoms on the concerted nature of the common reaction mechanism, involving a 6-center transition state complex as indicated in eq. Research, 5303 Wurenlingen, Switzerland. EGGER AND VITINSOf particular interest is the question of the extent of nonsynchronous bond breaking and bond formation, i.e., the amount of polar character in the ground and transition states.To this end we have so far reported measurements on N-allyl-N-cyclohexylamine [ 1 ] and triallylamine [2] and are presently investigating N-allyl-N-methylamine and N-allyl-N-methylaniline, as well as 1,6-hexadiene.Experimental Materials N-diallylamine (DAA) and toluene (T) (used as an internal standard) were obtained from Fluka Chemical Corporation, Buchs, Switzerland. After distillation, DAA was found by gas chromatography (GC) to be 99.0% pure, containing one major light impurity which proved to be thermally stable at the reaction conditions used and did not interfere in the analysis of the product mixture.Two starting mixtures (denoted by A and B ) with mole ratios DAA/T of 0.928 and 0.855, respectively, have been used. The mixtures were stored under nitrogen and gave GC analyses reproducible within =t0.6% over the period of several weeks.Methylamine, supplied by Fluka Chemical Corporation, was purified by distillation and stored as a gas in a 2-1. bulb. GC analyses showed it to be 98% pure. The observed impurities did not affect the analysis of the starting or product mixture. Apparatus and procedureThe static high vacuum system and general procedures used for the kinetic studies were essenti...

The kinetics of the thermal decomposition of hepta-1,6-diene (HD) have been studied in the gas phase over the temperature range 628-744 °K. Propylene and butadiene in essentially equimolar concentrations are the major reaction products, with 4-methylcyclohexene, cyclopentene, and ethylene as minor detectable side products at large conversions. First-order rate constants for the disappearance of HD, obtained by an internal standard technique, fit the Arrhenius relationship, log k, sec-1 = 11.31 ± 0.44 -(47.00 ± 0.73 kcal mol-1)/2.303R7. The reaction is homogeneous, and up to a 20-fold excess over HD of added but-l-ene, propylene, or toluene did not affect the rate constants. The entropy of activation derived from these data is AS* = -11.3, in excellent agreement with prediction. The extent of nonsynchronous bond breaking and the nature of the transition state involved in these reactions is discussed. The reaction is best described as a concerted "retro-ene" elimination of propylene.The observed activation parameters are in line with a cyclic six-center transition state and with the results obtained for similar reactions of compounds of the general structure (allyl)XYH, where X equals NR, O, CO, or CR2 and Y equals CR2 or O. An independent study of the kinetics of the thermal l decomposition of hepta-1,6-diene (HD) has not been reported to date. Ellis and Frey,3 when pyrolyzing bicyclo[3.2.0]heptane (BCH) observed a fast secondary reaction of the primary product HD, yielding propylene and butadiene in practically equimolar quantities.We have become interested in reaction 1 in connection with a series of investigations in this laboratory4•5 of the thermochemical kinetics involved in reactions of the general type (allyl)XYH ->-+ X==YBased on these studies it was to be expected, that n,-(n + 5)-diolefins should in principle be capable of undergoing a concerted 6-center "retro-ene" decomposition in analogy with allyl alkyl ethers,6 but-3-enoic acids,7 but-3-enols,8 and jV-allyl-jV-alkylamines.4 5 Furthermore, the absence of a heteroatom should yield interesting information regarding the nonsynchroneity involved in these reactions, i.e., the amount of charge separation in the six-center transition state. For

The gas phase thermal decomposition of triallylamine was studied in the temperature range 531 to 620 K. The major products observed in the reaction were propylene and 3‐picoline. The first order rate constants for depletion of triallylamine, obtained using the internal standard technique, are found to be independent of pressure and conversion, and fit the Arrheniusrelationship The reaction appears to be homogeneous, as a 15‐fold change in thc surface‐to‐volume ratio of the vessel left the rate constants unchanged. The Arrhenius parameters are consistent with a molecular elimination reaction involving a six‐center transition state, yielding propylene and N‐allyl‐prop‐2‐enaldimine. It is proposed that the latter product undergoes a 1,5‐hydrogen transfer, followed by a ring closure reaction to yield dihydropicoline, which in turn reacts forming 3‐picoline via a self‐initiated decomposition reaction.

The gas-phase unimolecular thermal decomposition of N-allyl-N-methylamine (AMA) w a s investigated in the temperature range 602-694 K. The principal products are propene and methylenearnine. First-order rate constants, calculated using the internal standard method, fit the Arrhenius relationship (i). The reaction appears log ( k J s -l ) = (1 1.37 f 0.56) -(43.38 f 1.62 kcal rn01-~)/2.3R7 5 0) to be homogeneous as a 15-fold change in surface :volume ratio of the reaction vessel yields no significant change in the rate constants. The decomposition of AMA follows a retro-' ene ' mechanism via a 6-centre transition state.The Arrhenius parameters for A M A decomposition are compared with those observed for other alkylallylamines.The significance of these observations in an evaluation of the extent of charge separation, i.e. non-synchronism, in the transition state is discussed.EARLIER studies of the thermal decomposition of Nsubstituted allylamines 1-3 have shown that reaction proceeds via a retro-' ene ' type mechanism analogous to the reactions of butenols,4y5 butenoic acid^,^^^ and certain olefins such as hepta-l,&diene,* involving a sis-centre transition state (Scheme 1

The thermal decomposition of ethylallylether (EAE) has been studied in the gas phase over the temperature range of 560-648'K.Propylene and acetaldehyde are the only reaction products observed. The reaction is apparently homogeneous in nature and independent of the pressure of EAE and of added foreign gases. The experimetally determined first-order rate constants, using the internal standard technique, fit the Arrhenius relationship log k(s-') = 11.84 + 0.29 -(43.57 =t 0.77 kcal/mole)/2.303RT, Independently the same rate constants are obtained, based on the amounts of products formed. The observed activation parameters are in general agreement with expectations based on the concept of a 6-center 1,5-H-shift retro-"ene" reaction mechanism, and they agree with previous results obtained for the similar reactions involving alkylallylamines and olefins. Previous shown in e q .