Kinetics and mechanism of thermal gas-phase elimination of ?-substituted carboxylic acids: role of relative basicity of ?-substituents and acidity of incipient proton

Gas‐phase pyrolysis mechanisms of 3‐anilino‐1‐propanol: Density functional theory study

“…The activation energy barrier of channel 1 is 54.48 kcal/mol at B3LYP/6‐31G (d, p) level (shown in Fig. 2), and this explains why the reaction could occur at high temperature only, which is consistent with the literature reports 5–8.…”

“…Compared with that of channel 3, the activation energy barrier of the reaction channel 2's rate‐determining step is lower, so this reaction channel occurs easily in these two channels. With the same pyrolytic products of different channels, on the basis of our calculation results, we can see that the activation energy barrier of the direct synergistic reaction is lower, and therefore, this channel is easier to occur, which is coincident with the experimental results 5, 8, though it is not consistent with the point of view that the energy barrier of the nonconcerted reaction pathway is lower than that of the direct concerted reaction 16–21. In all the channels, we conclude that the energy barrier of the pyrolysates P1, P2, and P3 is lower than that of pyrolysates P4 and P5, so this kind of reaction is generally easier to occur.…”

“…The α‐ and β‐( N ‐arylamino) propanoic acids, carboxylic acids, and 3‐amino propyl alcohols are all important materia medicas in medicine, and they also have very broad applications in many other fields 1–4. Al‐Awadi and coworkers have reported that the gas‐phase pyrolysis mechanisms of these compounds are similar 5–8. For example, the pyrolysate of 2‐ N ‐arylaminopropanoic acid showed the elimination products to be CO, CH 3 CHO, and aniline, while the pyrolysate of 3‐ N ‐arylaminopropanoic acid revealed the formation of acylic acid on aniline 6.…”

The kinetics and mechanisms of gas phase elimination of the ethyl ester of amino acid hydrochlorides

“…The acid product of these esters with a substituent at the a-position, under the reaction conditions, may further decompose into another products. In this respect, the gas phase elimination of several types of 2-substituted carboxylic acids [3][4][5][6][7][8][9] have been described, both experimentally and theoretically, in terms of a decarbonylation process as depicted in reaction (2).…”

“…However, 2-substituted amino carboxylic acids proceed a decarboxylation process as reported in the homogeneous, unimolecular gas phase pyrolysis of N,Ndimethylglycine, 10 picolinic acid, 11 and N-phenylglycine 12 [reaction (3)].…”