Microwave Spectrum and Barrier to Internal Rotation in CH3BF2

Naylor, Robert E.; Wilson, Edwin Bidwell

doi:10.1063/1.1743470

Cited by 94 publications

(13 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Not only are methyl C-H bonds expected to be of rather low acidity but, in general, methyl groups CH 3 -E (where E represents either C or O here) undergo extremely fast rotation about the C-E bonds even in the solid state, as shown by solid-state NMR spectroscopy (Riddell & Rogerson, 1996, 1997. In addition, so far as the methyl group in compound (IV) which contains atom C37 is concerned, it is well established (Tannenbaum et al, 1956;Naylor & Wilson, 1957) that sixfold rotational barriers to intramolecular rotation are extremely low; barriers of this type are encountered when a fragment of local C 3 symmetry (such as methyl or tertbutyl) is bonded to a fragment with effective local C 2 symmetry (such as a planar ring) and the heights of these barriers are typically just a few tens of J mol À1 . In the absence of any intermolecular hydrogen bonds, the molecules in both (III) and (IV) are linked into chains by means ofstacking interactions.…”

Section: Figurementioning

confidence: 99%

Four related esters: two 4-(aroylhydrazinyl)-3-nitrobenzoates and two 3-aryl-1,2,4-benzotriazine-6-carboxylates

et al. 2013

View full text Add to dashboard Cite

The molecules of both methyl 4-[2-(4-chlorobenzoyl)hydrazinyl]-3-nitrobenzoate, C15H12ClN3O5, (I), and methyl 4-[2-(2-fluorobenzoyl)hydrazinyl]-3-nitrobenzoate, C15H12FN3O5, (II), contain an intramolecular N-H···O hydrogen bond, and both show electronic polarization in the nitrated aryl ring. In both compounds, molecules are linked by a combination of N-H···O and C-H···O hydrogen bonds to form sheets, which are built from R4(3)(18) rings in (I) and from R4(4)(28) rings in (II). In each of methyl 3-phenyl-1,2,4-benzotriazine-6-carboxylate, C15H11N3O2, (III), and methyl 3-(4-methylphenyl)-1,2,4-benzotriazine-6-carboxylate, C16H13N3O2, (IV), the benzotriazine unit shows naphthalene-type delocalization. There are no hydrogen bonds in the structures of compounds (III) and (IV), but in both compounds, the molecules are linked into chains by π-π stacking interactions involving the benzotriazine units. The mechanism of chain formation is the same in both (III) and (IV), and the different orientations of the two chains can be related to the approximate relationship between the unit-cell metrics for (III) and (IV).

show abstract

Section: Figurementioning

confidence: 99%

Four related esters: two 4-(aroylhydrazinyl)-3-nitrobenzoates and two 3-aryl-1,2,4-benzotriazine-6-carboxylates

et al. 2013

View full text Add to dashboard Cite

show abstract

“…(iii) a single C-HÁ Á ÁO contact in (XXIV), where the C-H bond forms part of a methyl group: not only are such bonds of low acidity but sixfold barriers to intramolecular rotation, such as those for bonds between methyl groups and aryl rings, are generally very low (Tannenbaum et al, 1956;Naylor & Wilson, 1957); and (iv) all of the C-HÁ Á ÁF contacts in (VII), (Xb) and (XXII) and the single C-HÁ Á ÁCl contact in (XXII), since it is known (Howard et al, 1996;Brammer et al, 2001) that both F and Cl when bonded to C are extremely weak acceptors, particularly from C-H bonds.…”

Section: Supramolecular Aggregationmentioning

confidence: 99%

Patterns of hydrogen bonding in mono- and di-substituted N-arylpyrazinecarboxamides

Wardell

Souza

Vasconcelos

et al. 2008

Acta Crystallogr Sect B

View full text Add to dashboard Cite

The molecular and supramolecular structures of 18 N-arylpyrazinecarboxamides, Ar NHCO(C(4)H(3)N(2)), have been determined, including the stoichiometric monohydrate of N-(3-methoxyphenyl)pyrazinecarboxamide, and two polymorphs of N-(4-fluorophenyl)pyrazinecarboxamide having Z' values of 1 and 4, respectively. The aryl groups were selected to include the geometric isomers for a compact range of substituents, namely methyl, trifluoromethyl, fluoro, chloro, methoxy and nitro groups, which exhibit markedly varied electronic properties and markedly varied behaviour as hydrogen-bond donors and acceptors. However, not all isomers in each group could be structurally investigated. A small number of derivatives containing disubstituted aryl groups have also been included in this study. The crystal structures of the solvent-free carboxamides reported here exhibit a wide range of direction-specific intermolecular forces, including N-H...N, N-H...O, C-H...N and C-H...O hydrogen bonds, and pi...pi stacking interactions, while the structure of N-(3-methoxyphenyl)pyrazinecarboxamide monohydrate also contains O-H...N and O-H...O hydrogen bonds. The resulting supramolecular structures can be zero-, one- or two-dimensional, although no three-dimensional supramolecular aggregation has been observed. In the finite, zero-dimensional structures, pairs of molecules are linked by hydrogen bonds to form cyclic centrosymmetric dimers. The one-dimensional structures include chains formed by the pi-stacking of otherwise isolated molecules, simple chains generated by either C-H...O or C-H...N hydrogen bonds, and hydrogen-bonded chains of rings. The two-dimensional structures include examples of both pi-stacked hydrogen-bonded chains and hydrogen-bonded sheets.

show abstract

“…Not only are methyl C-H bonds expected to be of rather low acidity but, in general, methyl groups CH 3 -E undergo extremely fast rotation about the C-E bonds even in the solid state, as shown by solid-state NMR spectroscopy (Riddell & Rogerson, 1996. In addition, it is well known (Tannenbaum et al, 1956;Naylor & Wilson, 1957) that sixfold rotational barriers to intramolecular rotation are extremely low: barriers of this type are encountered when a fragment of local C 3 symmetry (such as methyl or tert-butyl) is bonded to a fragment with effective local C 2 symmetry (such as a planar ring) and the heights of these barriers are typically a few tens of J mol À1 . Contacts of the type C-HÁ Á Á occur in (VIII), (IX) and (XIV), while similar contacts of C-HÁ Á ÁO and C-HÁ Á ÁN types occur in (XIV).…”

Section: Crystal Structuresmentioning

confidence: 99%

Structural comparisons of isomeric series of 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines and 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines

Portilla

Quiroga

Nogueras

et al. 2008

Acta Crystallogr Sect B

View full text Add to dashboard Cite

The structures of three new 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines, 8-methyl-7-(4-chlorophenyl)-10-phenyl-6,10-dihydro-5H-benzo[h]pyrazolo[3,4-b]quinoline, C(27)H(20)ClN(3), 8-methyl-7-(3-pyridinyl)-10-phenyl-6,10-dihydro-5H-benzo[b]pyrazolo[3,4-b]quinoline, C(26)H(20)N(4), and 8-methyl-7-(4-pyridinyl)-10-phenyl-10H-benzo[h]pyrazolo[3,4-b]quinoline, C(26)H(18)N(4), which is an unexpected oxidation product isolated from the attempted synthesis of 8-methyl-7-(4-pyridinyl)-10-phenyl-6,10-dihydro-5H-benzo[h]pyrazolo[3,4-b]quinoline, and those of three new 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines, 11-(4-methylphenyl)-10-methyl-8-phenyl-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, C(28)H(23)N(3) (P\bar 1, Z' = 2), 11-(4-methoxyphenyl)-10-methyl-8-phenyl-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, C(28)H(23)N(3)O (P2(1)/c, Z' = 4), and 11-(3,4,5-trimethoxyphenyl)-10-methyl-8-phenyl-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, C(30)H(27)N(3)O(3), are reported. The crystal structures are compared with those of a number of analogues reported in the recent literature; in particular, structural comparisons are drawn within each series as the substituted pendent aryl group is varied, and between several pairs of strictly isomeric 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines and 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines containing the same aryl substituents within each pair. Intermolecular interactions of the C-H...pi type are found in the crystal structures of both series, but pi...pi stacking interactions are found only in the 7-aryl-benzo[h]pyrazolo[3,4-b]quinoline series.

show abstract

Microwave Spectrum and Barrier to Internal Rotation in CH3BF2

Cited by 94 publications

References 5 publications

Four related esters: two 4-(aroylhydrazinyl)-3-nitrobenzoates and two 3-aryl-1,2,4-benzotriazine-6-carboxylates

Four related esters: two 4-(aroylhydrazinyl)-3-nitrobenzoates and two 3-aryl-1,2,4-benzotriazine-6-carboxylates

Patterns of hydrogen bonding in mono- and di-substituted N-arylpyrazinecarboxamides

Structural comparisons of isomeric series of 7-aryl-benzo[h]pyrazolo[3,4-b]quinolines and 11-aryl-benzo[f]pyrazolo[3,4-b]quinolines

Contact Info

Product

Resources

About