The molecular structure of ammonia oxide (NH3O). An ab initio study

1977 ◽  
Vol 30 (4) ◽  
pp. 699 ◽  
Author(s):  
L Radom ◽  
JS Binkley ◽  
JA Pople
Keyword(s):  
Molecular Structure ◽  
Ab Initio ◽  
Bond Length ◽  
Basis Sets ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Trimethylamine Oxide ◽  
Polarization Functions ◽  
Split Valence ◽  
Calculated Bond Length

Ab initio molecular orbital theory is used to determine the molecular structure of ammonia oxide (NH3O). It is found that the N-O bond length is considerably overestimated by minimal (STO-3G), split-valence (4-31G and 6-31G) and large sp basis sets. This fault is rectified when polarization functions on nitrogen and oxygen are included in the basis (6-31G*) leading to the best theoretical value for the N-O length of 1.377 A. Electron correlation has little effect on the calculated bond length. Calculations (STO-3G and 4-31G) are also reported for trimethylamine oxide.

Structures of simple anions from ab initio molecular orbital calculations

1976 ◽  
Vol 29 (8) ◽  
pp. 1635 ◽  
Author(s):  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Basis Set ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Limited Information ◽  
Orbital Theory ◽  
Comparable Quality ◽  
Split Valence ◽  
Theoretical Results

Ab initio molecular orbital theory with the minimal STO-3G and split-valence 4-31G basis sets is used to obtain geometries of 18 anions:OH-, NH2-, HF2-, BH4-, BF4-, C22-, CN-, NCN2-, N3-, NO2-, NO3-, 0CCO2-, CO32-, HCOO-, CH3COO-, C2O42-, C4O42- and C(CN)3-. The theoretical results are compared with experimental results from the literature. The STO-3G basis set performs somewhat worse for anions than for neutral molecules. On the other hand, the 4-31G basis set gives good results and predicts bond lengths to within 0.02� for all the molecules considered. Limited information on bond angle predictions suggests that these are of comparable quality to those for neutral molecules. The tricyanomethanide ion is predicted to be planar.

An ab initio molecular orbital study of the structure and properties of propadienone (methyleneketene)

1978 ◽  
Vol 31 (1) ◽  
pp. 1 ◽  
Author(s):  
L Radom
Keyword(s):  
Carbon Monoxide ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Heat Of Formation ◽  
Basis Sets ◽  
Orbital Theory ◽  
Orbital Interactions ◽  
Planar Molecule ◽  
Split Valence ◽  
Acetylene Carbon

Ab initio molecular orbital theory with minimal (STO-3G) and split- valence (4-31G) basis sets has been used to obtain fully optimized structures for propadienone, allene, butatriene, carbon dioxide, ketene and vinylidene. Propadienone is predicted to be a planar molecule with C2V symmetry. The systematic deficiencies of the STO-3G and 4-31G basis sets have been taken into account in deriving a complete ro structure for propadienone. A striking feature of this structure is the HCH angle (117.°) which is about 5° smaller than the corresponding angle (122.3°) in ketene. An estimate (125 kJ mol-1) of the heat of formation of propadienone is reported. The alternating dipole moment magnitudes in the series H2CO, H2CCO and H2CCCO are explained in terms of orbital interactions. Propadienone is predicted to be considerably (about 135 kJ mol-1) more stable than vinylidene+carbon monoxide but slightly (about 10-20 kJ mol-1) less stable than acetylene+carbon monoxide.

Ab initio studies on amides: acetamide, N-methylformamide and N-methylacetamide

1982 ◽  
Vol 35 (6) ◽  
pp. 1071 ◽  
Author(s):  
L Radom ◽  
NV Riggs
Keyword(s):  
Ab Initio ◽  
Internal Rotation ◽  
Molecular Orbital ◽  
Basis Sets ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Methyl Group ◽  
Barriers To Internal Rotation ◽  
Reported Data

Ab initio molecular orbital theory with the STO-3G and 4-31G basis sets has been used to investigate the geometries, preferred conformations, and barriers to internal rotation for acetamide, N-methylformamide and N-methylacetamide. Results are compared with corresponding previously reported data for formamide. For acetamide, the preferred conformation has the methyl group staggered with respect to the N-C bond whereas for N-methylformamide the methyl group is eclipsed with respect to this bond. Both N-methylformamide and N-methylacetamide prefer a Z-arrangement, i.e. methyl cis to C=O about the N-C bond. Experimentally determined barriers to internal rotation about the N-C bond generally lie within the range spanned by the STO-3G and 4-31G estimates.

Approximate Molecular Orbital Theory: The Hückel/Tight-binding Model

2020 ◽  
pp. 231-245
Author(s):  
Jochen Autschbach
Keyword(s):  
Bond Length ◽  
Molecular Orbital ◽  
Tight Binding ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Bond Length Alternation ◽  
Binding Model ◽  
Linear Polyenes ◽  
Benzene Structure ◽  
Cyclic Polyenes

Huckel molecular orbital (HMO) theory is a simple approximate parameterized molecular orbital (MO) theory that has been very successful in organic chemistry and other fields. This chapter introduces the approximations made in HMO theory, and then treats as examples ethane, hetratriene and other linear polyenes, and benzene and other cyclic polyenes. The pi binding energy of benzene is particularly large according to HMO theory, rationalizing the special ‘aromatic’ behaviour of benzene. But there is a lot more to benzene than that. It is shown that the pi bond framework of benzene would rather prefer a structure with alternating single and double C-C bonds, rather than the actually observed 6-fold symmetric structure where all C-C bonds are equivalent. The observed benzene structure is a result of a delicate balance between the tendencies of the pi framework to create bond length alternation, and the sigma framework to resist bond length alternation.

ChemInform Abstract: MOLECULAR ORBITAL THEORY OF THE PROPERTIES OF INORGANIC AND ORGANOMETALLIC COMPOUNDS. 2. STO-NG BASIS SETS FOR FOURTH-ROW MAIN-GROUP ELEMENTS

1982 ◽  
Vol 13 (4) ◽  
Author(s):  
W. J. PIETRO ◽  
E. S. BLUROCK ◽  
R. F. JUN. HOUT ◽  
W. J. HEHRE ◽  
D. J. DEFREES ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Organometallic Compounds ◽  
Main Group ◽  
Basis Sets ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Main Group Elements

Ab initio molecular orbital theory

1986 ◽  
Vol 119 (2) ◽  
pp. 234 ◽  
Author(s):  
Luigi Olcari
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Theory ◽  
Orbital Theory

The Heat of Formation of Formaldimine

1992 ◽  
Vol 45 (1) ◽  
pp. 285 ◽  
Author(s):  
BJ Smith ◽  
JA Pople ◽  
LA Curtiss ◽  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Heat Of Formation ◽  
Molecular Orbital Theory ◽  
Orbital Theory

Ab initio molecular orbital theory at the G 2 level has been used to predict new values for the heat of formation of formaldimine (CH2=NH): ?Hfº0 = 94 ±10 kJ mol-1 and ?Hfº298 = 86 ±10 kJ mol-1.

scholarly journals Ab initio study regarding the evaluation of the antioxidant character of cyanidin, delphinidin and malvidin

2012 ◽  
Vol 10 (1) ◽  
pp. 180-186 ◽  
Author(s):  
Raluca Pop ◽  
Mariana Ştefănut ◽  
Adina Căta ◽  
Cristian Tănasie ◽  
Mihai Medeleanu
Keyword(s):  
Ab Initio ◽  
Theoretical Study ◽  
Molecular Descriptors ◽  
Frontier Molecular Orbital ◽  
Hydroxyl Groups ◽  
Molecular Orbital Theory ◽  
Ab Initio Study ◽  
Wide Spread ◽  
Orbital Theory ◽  
Dissociation Enthalpy

AbstractA theoretical study regarding the evaluation of the antioxidant character of three of the most wide-spread anthocyanidins (cyanidin, delphinidin and malvidin) was carried out at ab initio level. Different parameters (bond dissociation enthalpy, ionization potential, proton affinity, and electron transfer enthalpy) were computed for each OH group of the compounds in order to predict their antioxidant capacity. Several molecular descriptors based on frontier molecular orbital theory (hardness, electrophilicity, frontier charge density) were also calculated, as well as the atomic charges corresponding to the O atoms of the hydroxyl groups.

Enthalpies of Formation of Gas-Phase N3, N3-, N5+, and N5-from Ab Initio Molecular Orbital Theory, Stability Predictions for N5+N3-and N5+N5-, and Experimental Evidence for the Instability of N5+N3-

2004 ◽  
Vol 126 (3) ◽  
pp. 834-843 ◽  
Author(s):  
David A. Dixon ◽  
David Feller ◽  
Karl O. Christe ◽  
William W. Wilson ◽  
Ashwani Vij ◽  
...  
Keyword(s):  
Ab Initio ◽  
Experimental Evidence ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Enthalpies Of Formation ◽  
Molecular Orbital Theory ◽  
Orbital Theory
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