Molecular Structure, Intramolecular Hydrogen Bonding, Solvent-Induced Isomerization, and Tautomerism in Azolylmethylidene Derivatives of 2-Indanone

2017 ◽  
Vol 2017 (10) ◽  
pp. 1353-1364 ◽  
Author(s):  
Mark V. Sigalov ◽  
Bagrat A. Shainyan ◽  
Nina N. Chipanina ◽  
Larisa P. Oznobikhina
Keyword(s):  
Molecular Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

Beziehungen zwischen Rotationsisomerie, Wasserstoffbrücken-Bindung und Substituenteneffekten der organischen Chemie / Relations between Rotational Isomerism, Hydrogen Bonding, and Substituent Effects in Organic Chemistry

1972 ◽  
Vol 27 (6) ◽  
pp. 663-674 ◽  
Author(s):  
Gotthard H. Krause ◽  
Herbert Hoyer
Keyword(s):  
Hydrogen Bonding ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Proton Acceptor ◽  
Single Bond ◽  
Free Enthalpy ◽  
Acceptor Group ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

The change of free enthalpy involved in intramolecular hydrogen bonding is smaller if the proton acceptor group can rotate round a single bond, as compared to proton acceptor groups which are fixed in a position optimal for hydrogen bonding. Also, the free enthalpy change is altered when the rotation of the proton acceptor is sterically restricted. This is demonstrated by comparing the absorptions of carbonyl stretching vibrations in the infrared spectra of certain compounds showing rotational isomerism. In the present study derivatives of 5-hydroxy-2,2-dimethyl-6-carbomethoxychromanone- (4), 3-nitrosalicylaldehyde and 3-nitro-2-hydroxy-acetophenones substituted in the position 5 and 6 are examined.

Molecular and crystal structure of azadirachtin-H

1996 ◽  
Vol 52 (1) ◽  
pp. 145-150 ◽  
Author(s):  
T. R. Govindachari ◽  
Geetha Gopalakrishnan ◽  
S. S. Rajan ◽  
V. Kabaleeswaran ◽  
L. Lessinger
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Hydroxyl Group ◽  
Inhibiting Activity ◽  
Nmr Studies ◽  
Rotation Axes ◽  
Intramolecular Hydrogen ◽  
Azadirachtin A

Azadirachtin-H, isolated from the seed kernels of Azadirachta indica (neem), crystallizes in space group I4, Z = 8, with disordered ethyl acetate solvent filling channels along the fourfold rotation axes. The crystal structure determination showed that the previously reported molecular structure deduced from NMR studies was correct except for the stereochemistry at C(11). Azadirachtin-H, which belongs to a group of C-seco-tetranortriterpenoids (C-seco-limonoids) of great interest for their insect antifeedant and ecdysis-inhibiting activity, has some unusual features: the absence of a carbomethoxy group at C(11); the presence of a cyclic hemiacetal function at C(11); the α-orientation of the hydroxyl group on C(11), opposite to that in all other known azadirachtins with a hydroxyl group on C(11), except azadirachtin-I. There is no intramolecular hydrogen bonding. In this crystal the rotation of the two major moieties of the azadirachtin-H molecule about the single connecting C(8)—C(14) bond is quite different from that in azadirachtin-A, whose crystal structure has recently been determined.

Molecular Structure and Photoinduced Intramolecular Hydrogen Bonding in 2-Pyrrolylmethylidene Cycloalkanones

2015 ◽  
Vol 80 (21) ◽  
pp. 10521-10535 ◽  
Author(s):  
Mark Sigalov ◽  
Bagrat Shainyan ◽  
Nina Chipanina ◽  
Larisa Oznobikhina ◽  
Natalia Strashnikova ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen

Photochemical reactions of azo compounds. X. Photochemical properties of azobenzene-2-carboxylic acids

1967 ◽  
Vol 20 (5) ◽  
pp. 929 ◽  
Author(s):  
CP Joshua ◽  
GE Lewis
Keyword(s):  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Intramolecular Hydrogen Bonding ◽  
Photochemical Reactions ◽  
Azo Compounds ◽  
Neutral Compounds ◽  
Methyl Derivatives ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

Two chloro and two methyl derivatives of azobenzene-2-carboxylic acid have been found to yield the corresponding derivatives of benzo[c]cinnoline-4- carboxylic acid in good yields when irradiated in 98% sulphuric acid. The question of intramolecular hydrogen bonding in relation to the properties of azobenzene-2-carboxylic acids is discussed. Infrared absorption spectra of the neutral compounds have provided confirmation of internal hydrogen bonding. Attempts to prepare the cis isomers of these azo compounds have been unsuccessful.

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