Hydrogen-bonded carbonyl groups

The most decisive support for this contention has proceeded from the X-ray study of crystalline sperm whale myoglobin, which, as Kendrew has demonstrated (Kendrew et al., 1960, 1961), contains 118 of its 153 residues, that is, 77 %, in right-handed a-helices. The side chains of L-amino acids in a right-handed helix project in a direction opposite to that of carbonyl groups hydrogen-bonded into the helix, an orientation that is in fact... 

Sample Solution (a) Enolization in p-dicarbonyl compounds involves the carbon between the two carbonyl groups. Hydrogen bonding occurs between OH and C=0. 

Overall the reaction is classified as an addition Water adds to the carbonyl group Hydrogen becomes bonded to the negatively polarized carbonyl oxygen hydroxyl to the positively polarized carbon... 

On the other hand, the group of No wick [29] developed polyurea templates with the general structure 35 in order to nucleate parallel /1-sheet structures. They reported that in a model compound (36) the urethane carbonyls are hydrogen bonding to the adjacent NH and that the orientation of the bonding interactions is controlled by the size of the end substituent, in this case a phenyl group. They also recently prepared 37 and showed by NMR that it adopts mostly the proposed parallel /1-sheet conformation in chloroform [30]. 

In aldehydes the carbonyl group is bonded to at least one hydrogen atom, as in formaldehyde,... 

The aryl radical adds to the carbonyl group, a bond cleaves, and the resulting radical abstracts hydrogen from tri- -butyltin hydride to form the product and a new chain-carrying radical. 

P sheet A mode of protein folding in which two polypeptide chains (/ strands) lie side by side and either parallel or antiparallel with respect to the direction of the NH-Cq-CO group. Hydrogen bonds are formed from a carbonyl group of one chain to an amide nitrogen atom of the other chain and vice versa. 

While a nickel boride catalyst preferentially saturates the carbon-carbon double bond of a,p-unsaturated aldehydes, the cobalt borides have a tendency to favor carbonyl group hydrogenation. Cinnamaldehyde was hydrogenated to cinnamoyl alcohol in 97% selectivity at 50% conversion and 86% selectivity at 74% conversion over a P-2 cobalt boride (Eqn. 12.7).5 With a P-2W cobalt boride the unsaturated alcohol was produced in 97% selectivity at 73% conversion. The presence of the aromatic ring enhances selectivity in this reaction since the hydrogenation of crotonaldehyde to 2-buten-l-ol occurred with only about a 25% selectivity at under 20% conversion over either catalyst (Eqn. 12.8).54... 

The selective hydrogenation of the double bond of an a,p-unsaturated carbonyl compound is rather easily accomplished over most metal catalysts under moderate conditions. Because double bond isomerization does not take place in these systems, palladium catalysts are often used in the liquid phase at ambient temperature and atmospheric pressure. An added advantage here is that palladium is essentially inert for aliphatic aldehyde and ketone hydrogenations under these conditions. Vapor phase hydrogenations should be run at temperatures as low as possible to minimize carbonyl group hydrogenations. Catalysts such as Ni(B) are... 

The combination of amine groups, which are basic, and urea groups, which are hydrogen-bond donors, is an example of cooperativity via dual nucleophilic/electro-philic activation. The activation of carbonyls via hydrogen bonding to urea is very... 

The carbon atoms on either side of the carbonyl group are bonded to other atoms. The simplest ketone has only hydrogen atoms bonded to the side carbons, as shown in the following diagram. The common name of this ketone is acetone. 

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