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In computational biology, protein pK a calculations are used to estimate the pK a values of amino acids as they exist within proteins.These calculations complement the pK a values reported for amino acids in their free state, and are used frequently within the fields of molecular modeling, structural bioinformatics, and computational biology.
The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.
An electron donating group (EDG) or electron releasing group (ERG, Z in structural formulas) is an atom or functional group that donates some of its electron density into a conjugated π system via resonance (mesomerism) or inductive effects (or induction)—called +M or +I effects, respectively—thus making the π system more nucleophilic.
Pauling's second rule is that the value of the first pK a for acids of the formula XO m (OH) n depends primarily on the number of oxo groups m, and is approximately independent of the number of hydroxy groups n, and also of the central atom X. Approximate values of pK a are 8 for m = 0, 2 for m = 1, −3 for m = 2 and < −10 for m = 3. [28]
The −OH group is replaced by an −NH 2 group and the =O group is replaced by =N R, giving amidines the general structure R n E(=NR)NR 2. [ 10 ] [ 11 ] [ 12 ] When the parent oxoacid is a carboxylic acid , the resulting amidine is a carboxamidine or carboximidamide ( IUPAC name).
A general linear imide functional group. In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. [1] The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis.
Its adjectival form, vinylogous, is used to describe functional groups in which the standard moieties of the group are separated by a carbon–carbon double bond. For example, a carboxylic acid is defined as a carbonyl group ( C=O ) directly attached to a hydroxyl group ( OH ): O=C–OH.
The benzoyl functional group. In organic chemistry, benzoyl (/ ˈ b ɛ n z oʊ ɪ l /, BENZ-oh-il) [1] is the functional group with the formula −COC 6 H 5 and structure −C(=O)−C 6 H 5. [2] [3] It can be viewed as benzaldehyde missing one hydrogen. The benzoyl group has a mass of 105 amu.