A theoretical study of intramolecular Diels-Alder and 1,3-dipolar cycloaddition stereoselectivity using ab initio methods, semiempirical methods, and a tandem quantum mechanic-molecular mechanic method

1992 ◽  
Vol 57 (18) ◽  
pp. 4862-4869 ◽  
Author(s):  
Frank K. Brown ◽  
U. Chandra Singh ◽  
Peter A. Kollman ◽  
Laura Raimondi ◽  
K. N. Houk ◽  
...  
Keyword(s):  
Quantum Mechanic ◽  
Ab Initio ◽  
Theoretical Study ◽  
Molecular Mechanic ◽  
Diels Alder ◽  
Semiempirical Methods ◽  
Dipolar Cycloaddition ◽  
Ab Initio Methods ◽  
Mechanic Method ◽  
Molecular Mechanic Method

On the possibility of conversion of strained bridgehead alkenes into carbenes via 1,2 hydrogen and 1,2 carbon migrations. A theoretical study of the rearrangements in the adamantene and protoadamantene systems

1998 ◽  
Vol 76 (6) ◽  
pp. 851-861 ◽  
Author(s):  
Gennady V Shustov ◽  
Michael TH Liu
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Theoretical Study ◽  
Activation Barrier ◽  
Main Channel ◽  
Diels Alder ◽  
Activation Barriers ◽  
Ab Initio Computation ◽  
Carbon Migration ◽  
High Level

Rearrangements of 2-adamantene 3, adamantylidene 4, and 4-protoadamantylidene 5 have been studied theoretically using high level ab initio computations. Adamantene 3 and adamantylidene 4 have singlet ground states. The conversion of 3 into 4 via 1,2 hydrogen migration ( Δ Gdouble dagger = 69.1 kcal mol-1) cannot compete with 1,2 carbon migration of 3 to 5 (30.3 kcal mol-1). The singlet carbene 5 rearranges to 2,4-dehydroadamantane 6 and 4,5-protoadamantene 9 via 1,3H and 1,2H shifts, respectively, with identical activation barriers of 8.8 kcal mol-1. The 1,2 migration of the bridge hydrogen in 5 leading to 3,4 protoadamantene 8 has a higher activation barrier (37.2 kcal mol-1). A retro Diels-Alder cycloaddition of 3 to 5-allyl-3-methylenecyclohex-1-ene 7 is the main channel of the unimolecular conversion of 3 ( Δ Gdouble dagger = 20.5 kcal mol-1). A predicted ratio of 7 > > 6 approx 9 of the products of thermolysis of 3 is in agreement with experimental data. The rearrangement of 4 into 6 via the 1,3H shift ( Δ Gdouble dagger = 11.8 kcal mol-1) dominates over the 1,2C shift of 4 to 8 (13.5 kcal mol-1), also in accord with experiment.Key words: adamantene, protoadamantenes, carbenes, rearrangements, ab initio, computation.

AB-INITIO THEORETICAL APPROACHES TO THE STRUCTURAL, ELECTRONIC AND VIBRATIONAL PROPERTIES OF SMALL CLUSTERS AND FULLERENES: THE STATE OF THE ART

1993 ◽  
Vol 04 (02) ◽  
pp. 227-237
Author(s):  
WANDA ANDREONI
Keyword(s):  
Ab Initio ◽  
Vibrational Spectra ◽  
Theoretical Study ◽  
State Of The Art ◽  
Electronic States ◽  
Vibrational Properties ◽  
Ab Initio Methods ◽  
Excited Electronic States ◽  
Theoretical Approaches ◽  
Small Clusters

A brief report is presented of recent advances in the theoretical study of clusters and fullerenes with ab-initio methods. Selected calculations of structural properties, excited electronic states and vibrational spectra will be discussed. The purpose is to compare different methods and clarify their specific powers and weaknesses.

scholarly journals Complexes of Formaldehyde and α-Dicarbonyls with Hydroxylamine: FTIR Matrix Isolation and Theoretical Study

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1144
Author(s):  
Barbara Golec ◽  
Magdalena Sałdyka ◽  
Zofia Mielke
Keyword(s):  
Ab Initio ◽  
Ftir Spectroscopy ◽  
Theoretical Study ◽  
Matrix Isolation ◽  
Ab Initio Methods ◽  
Spectra Analysis ◽  
Planar Complex ◽  
Solid Nitrogen ◽  
Solid Argon ◽  
Bonded Complexes

The interactions of formaldehyde (FA), glyoxal (Gly) and methylglyoxal (MGly) with hydroxylamine (HA) isolated in solid argon and nitrogen were studied using FTIR spectroscopy and ab initio methods. The spectra analysis indicates the formation of two types of hydrogen-bonded complexes between carbonyl and hydroxylamine in the studied matrices. The cyclic planar complexes are stabilized by O–H⋯O(C), and C–H⋯N interactions and the nonplanar complexes are stabilized by O–H⋯O(C) bond. Formaldehyde was found to form with hydroxylamine, the cyclic planar complex and methylglyoxal, the nonplanar one in both argon and nitrogen matrices. In turn, glyoxal forms with hydroxylamine the most stable nonplanar complex in solid argon, whereas in solid nitrogen, both types of the complex are formed.

A theoretical study, using ab initio methods, of tautomerism in 3-amino-1,2,4-triazole in the gas phase and in aqueous solution

1992 ◽  
pp. 1681 ◽  
Author(s):  
Oswald G. Parchment ◽  
Ian H. Hillier ◽  
Darren V. S. Green ◽  
Neil A. Burton ◽  
John O. Morley ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Ab Initio ◽  
Gas Phase ◽  
Theoretical Study ◽  
Ab Initio Methods

scholarly journals Nanobiological studies on drug design using molecular mechanic method

2015 ◽  
Vol 4 (1) ◽  
pp. 219
Author(s):  
Maryam Mousavi ◽  
Reza Rasoolzadeh ◽  
Zahra Hosseini ◽  
Mahmood Araghi ◽  
HooriaSeyedhosseini Ghaheh
Keyword(s):  
Drug Design ◽  
Molecular Mechanic ◽  
Mechanic Method ◽  
Molecular Mechanic Method
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