Remote carboxyl groups

Presence of water in the reaction mixture has significant importance because dihydrates crystallized in both cases. Single crystal X-ray analysis of (6)-3b-DBTACa.2H20 confirmed that one of the water molecules coordinated to the central calcium ion while the other one sticked to the remote carboxylic group by H-bond as it is showed in Scheme 3. [24]... 

A similar fast reduction was found with such ligands even if the remote carboxyl group was converted to the amide. Since the rate constants were not appreciably pH dependent, it is unlikely that the attack was at the ring nitrogen, which would be protonated. The reduction by is stoichiometric with these ligands, but the Eu reduces the ligands to some extent 104). 

In methylenechloride/trifluoroacetic acid or fluorsulfonic acid trifluoracetoxyl-ation (Eq. 44) [353] or fluorsulfonation[354] of the alkyl chain remote from the proton-ated carboxyl group occurs. 

It was our decision to combine two diacid units with a diamine as shown in Eq. (1) that gave the solution to the problem. The diamine acts. as a spacer group that converts two U-shaped subunits into a C-shaped molecule 6 which now involves a near perfect focus of two carboxyl groups. Enforcing this shape, rather than the S-shape 7 which is also possible can be accomplished by further remote structural elements. 

The neutral carboxyl group is not very effective in increasing the reduction rate of the complex. However, when the proton is removed from the carboxyl, the effect can increase and is greatest when the carboxyl ion is in a configuration favorable to chelation. Thus, the inverse (H+) path is not even observable for acid succinate in the same acidity range as that for which this path is important in the acid malonato reaction. The acid dissociation constants are known well enough so that the behavior difference between acid malonato and acid succinato can not be entirely ascribed to different acidities of the complexes. The results obtained with the acid malonate complexes, as reported in Table II, incidentally provide no support for the hypothesis (22) that electron transfer takes place by remote attack across hydrogen bonds. 

Invoking the reducibility of the ligand in certain instances helps explain some other comparisons. Thus, it has been a matter of concern that electron transfer by remote attack through an esterified carboxyl group is accompained by such drastic effects as hydrolysis of the ester, while electron transfer through a carbonyl, when this is part of a ketonic or aldehydic function, takes place easily. This occurs even though there are no opportunities here for the kind of chemistry which accompanies... 

When the substituent is more remote from the carboxyl group than in substituted benzoate esters, smaller values of p are to be expected. Thus, p — 1.21 for the alkaline hydrolysis of orf/io-substituted ethyl cinnamates, ArCH=CHCOOEt, in 87.8% aqueous ethanol at 30°C148 149. 

Certain functional groups can be accommodated during HI addition. While alcohols are converted to alkyl iodides under the usual reaction conditions,181 sulfones present no problems.133 134 Remote carboxylic acid functionality has no effect on the addition of HI,182 and a,3-unsaturated carboxylic acids produce good yields of exclusively the 3-iodocarboxylic acids, no matter what the substitution pattern about the C—C double bond (equation 136).114,140,183-186... 

Oxidation is oxidation of the carbon atom most remote from the carboxyl group in a fatty acid. The basic reaction, catalyzed by a monooxygenase that requires NADPH, O2, and cytochrome P-450, is shown below. It has been observed in liver microsomes and some bacteria. 

Inductive effects fall off rapidly as the number of a bonds between the carboxyl group and the substituent increases. Consequently, the acid-strengthening effect of a halogen decreases as it becomes more remote from the carboxyl group ... 

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