The conformational space of methacrylamide was explored by quantum mechanical modeling and surveyed in the 59.6–104.0 GHz frequency range using a millimeter-wave Stark-modulated free-jet absorption spectrometer. According to the relative orientation of the two unsaturated bonds, two conformers were observed, namely s-trans (A=5234.360(1), B=3364.9717(8) and C=2173.099(1) MHz) and s-cis (A=5207.292(1), B=3470.930(1) and C=2113.496(1) MHz). The s-trans conformation is the global minimum, with relative energy 4(2) kJ mol−1 and calculated isomerization barrier 15 kJ mol−1. Except for the methyl hydrogen atoms, s-cis-methacrylamide is planar and its methyl internal rotation barrier is 10.2(1) kJ mol−1. In s-trans-methacrylamide the allyl and amino frames form a dihedral angle of about 30° and the methyl internal rotation barrier is 7.4 kJ mol−1. This different behaviour is explained in terms of attractive and repulsive intramolecular interactions between groups: CH2/CO and CH3/NH2 for s-cis, CH2/NH2 and CH3/CO for s-trans. The tunneling splitting related to the double-well potential describing the interconversion between the two equivalent s-trans forms is 837.97(2) MHz and was reproduced by a one-dimensional flexible model using a 3.6 kJ mol−1 interconversion barrier.
Structure and dynamics of methacrylamide, a computational and free-jet rotational spectroscopic study / Maris A.; Melandri S.; Evangelisti L.; Vigorito A.; Sigismondi S.; Calabrese C.; Usabiaga I.. - In: JOURNAL OF MOLECULAR STRUCTURE. - ISSN 0022-2860. - STAMPA. - 1248:(2022), pp. 131391.1-131391.14. [10.1016/j.molstruc.2021.131391]
Structure and dynamics of methacrylamide, a computational and free-jet rotational spectroscopic study
Maris A.
Primo
;Melandri S.Secondo
;Evangelisti L.;Vigorito A.;Sigismondi S.;Calabrese C.;
2022
Abstract
The conformational space of methacrylamide was explored by quantum mechanical modeling and surveyed in the 59.6–104.0 GHz frequency range using a millimeter-wave Stark-modulated free-jet absorption spectrometer. According to the relative orientation of the two unsaturated bonds, two conformers were observed, namely s-trans (A=5234.360(1), B=3364.9717(8) and C=2173.099(1) MHz) and s-cis (A=5207.292(1), B=3470.930(1) and C=2113.496(1) MHz). The s-trans conformation is the global minimum, with relative energy 4(2) kJ mol−1 and calculated isomerization barrier 15 kJ mol−1. Except for the methyl hydrogen atoms, s-cis-methacrylamide is planar and its methyl internal rotation barrier is 10.2(1) kJ mol−1. In s-trans-methacrylamide the allyl and amino frames form a dihedral angle of about 30° and the methyl internal rotation barrier is 7.4 kJ mol−1. This different behaviour is explained in terms of attractive and repulsive intramolecular interactions between groups: CH2/CO and CH3/NH2 for s-cis, CH2/NH2 and CH3/CO for s-trans. The tunneling splitting related to the double-well potential describing the interconversion between the two equivalent s-trans forms is 837.97(2) MHz and was reproduced by a one-dimensional flexible model using a 3.6 kJ mol−1 interconversion barrier.File | Dimensione | Formato | |
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118_2022_methacrylamide.pdf
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