TY - JOUR
T1 - Substituent effects in the tautomerization of imidic acids R−C(OH)=NH → R−C(O)NH2
T2 - Kinetic implications for the formation of peptide bonds in the interstellar medium
AU - Würmel, Judith
AU - Simmie, John M.
N1 - Publisher Copyright:
© 2023 The Authors. International Journal of Chemical Kinetics published by Wiley Periodicals LLC.
PY - 2023/7
Y1 - 2023/7
N2 - A number of amides, RC(O)NH2, have been detected spectroscopically in the space between the stars. Naturally the study of how these are formed is an important question on the path of chemical evolution from the elements C, H, N, O, P, … to life because the so-called peptide-bond −C(O)−NH− is a key linkage in poly-amino acids or proteins. Both cyanides and water are abundant in the interstellar medium (ISM) and it has been suggested [J Phys Chem A. 2021;126:924-939] that these react on water–ice grains, catalyzed by acid H3O+, to form firstly imidic acids R−C≡ N + H2O → RC(OH)NH and subsequently to amides. Here we explore the kinetics in the gas-phase of the intramolecular tautomerization reaction of the imidic acids for R = H, HO, NC, H2N, HC(O), H3C, HOCH2, H2CCH,H3C(O), H2NCH2, C2H5, and CN, particularly at low temperatures where quantum mechanical small curvature and quantized reactant states tunneling are dominant. The most reactive imidic acid is H2NC(OH)NH which goes on to form urea, one of three known amides in the interstellar medium (ISM), which can self-react to form cytosine and uracil two canonical nucleobases in RNA. The thermochemistry ((Formula presented.), (Formula presented.), (Formula presented.), (Formula presented.)) of the imidic acids and amides is also reported as well as the tautomerization of sulfur and phosphorus analogs HC(SH)NH and HC(OH)PH.
AB - A number of amides, RC(O)NH2, have been detected spectroscopically in the space between the stars. Naturally the study of how these are formed is an important question on the path of chemical evolution from the elements C, H, N, O, P, … to life because the so-called peptide-bond −C(O)−NH− is a key linkage in poly-amino acids or proteins. Both cyanides and water are abundant in the interstellar medium (ISM) and it has been suggested [J Phys Chem A. 2021;126:924-939] that these react on water–ice grains, catalyzed by acid H3O+, to form firstly imidic acids R−C≡ N + H2O → RC(OH)NH and subsequently to amides. Here we explore the kinetics in the gas-phase of the intramolecular tautomerization reaction of the imidic acids for R = H, HO, NC, H2N, HC(O), H3C, HOCH2, H2CCH,H3C(O), H2NCH2, C2H5, and CN, particularly at low temperatures where quantum mechanical small curvature and quantized reactant states tunneling are dominant. The most reactive imidic acid is H2NC(OH)NH which goes on to form urea, one of three known amides in the interstellar medium (ISM), which can self-react to form cytosine and uracil two canonical nucleobases in RNA. The thermochemistry ((Formula presented.), (Formula presented.), (Formula presented.), (Formula presented.)) of the imidic acids and amides is also reported as well as the tautomerization of sulfur and phosphorus analogs HC(SH)NH and HC(OH)PH.
KW - amides
KW - chemical kinetics
KW - imidic acids
KW - tautomerization reaction
KW - thermochemistry
UR - http://www.scopus.com/inward/record.url?scp=85153533168&partnerID=8YFLogxK
U2 - 10.1002/kin.21642
DO - 10.1002/kin.21642
M3 - Article
AN - SCOPUS:85153533168
SN - 0538-8066
VL - 55
SP - 381
EP - 391
JO - International Journal of Chemical Kinetics
JF - International Journal of Chemical Kinetics
IS - 7
ER -