By the carboxylate group

Synthetic phenol capacity in the United States was reported to be ca 1.6 x 10 t/yr in 1989 (206), almost completely based on the cumene process (see Cumene Phenol). Some synthetic phenol [108-95-2] is made from toluene by a process developed by The Dow Chemical Company (2,299—301). Toluene [108-88-3] is oxidized to benzoic acid in a conventional LPO process. Liquid-phase oxidative decarboxylation with a copper-containing catalyst gives phenol in high yield (2,299—304). The phenoHc hydroxyl group is located ortho to the position previously occupied by the carboxyl group of benzoic acid (2,299,301,305). This provides a means to produce meta-substituted phenols otherwise difficult to make (2,306). VPOs for the oxidative decarboxylation of benzoic acid have also been reported (2,307—309). Although the mechanism appears to be similar to the LPO scheme (309), the VPO reaction is reported not to work for toluic acids (310). 

The existence of n-complex intermediates can be inferred from experiments in which they are trapped by nucleophiles under special circumstances. For example, treatment of the acid 1 with bromine gives the cyclohexadienyl lactone 2. This product results from capture of the n-complex by intramolecular nucleophilic attack by the carboxylate group ... 

Chymotrypsin shows a strong preference for hydrolyzing peptide bonds formed by the carboxyl groups of the aromatic amino acids, phenylalanine, tyrosine, and tryptophan. Flowever, over time chymotrypsin also hydrolyzes amide bonds involving amino acids other than Phe, Tyr, or Trp. Peptide bonds having leucine-donated carboxyls become particularly susceptible. Thus, the specificity... 

Task (3) is more difficult. It uses a series of reagents each of which is capable of breaking only certain amide bonds. One of these reagents is the enzyme trypsin, which breaks only those bonds formed by the carboxyl groups in arginine and lysine. It would break the polypeptide... 

In most cases the microspheres were insoluble. The polysaccharides might be partially cross-linked via amido groups formed by the carboxyl groups of the polyanion and the restored free amino group of chitosan. The susceptibility to enzymatic hydrolysis by lysozyme was poor, mainly because lysozyme, a strongly cationic protein, can be inactivated by anionic polysaccharides [207]. 

Broadly speaking, in the study of AB cements derived from poly-carboxylic acids, the band of interest falls in the region 1550-1620 cm (Mehrota Bohra, 1983 Bellamy, 1975). This band is the asymmetric stretch of the carboxylate group and its exact position depends on both the nature of the bonding involved (i.e. whether purely ionic or partially covalent), and the nature of any chelation by the carboxylate group (Bellamy, 1975). 

H. l Intramolecular general acid catalysis by the carboxyl group 271, H.2 Intra-... 

The contrasting effects of structural variation on EM for nucleophilic vs. general base catalysis by the carboxyl group ... 

With the important exception of acetals (and possibly certain other derivatives) of salicylic acid (compounds H. 1.6-11 see the following section), which are hydrolysed with intramolecular general acid catalysis by the carboxyl group, with EM s of the order of 104 M... 

A.5 Intramolecular nucleophilic catalysis by the carboxyl group of the hydrolysis ofphosphate andphosphonate esters... 

R was varied. Since the mechanism for the methyl ester is certainly A-1 and since intramolecular general acid catalysis should give a different transition state structure and therefore a different p value, it was concluded that the mechanism was A-1 in both cases. The rate enhancement provided by the carboxyl group substituent was ascribed to electrostatic catalysis whereby a proton is stabilized on the acetal oxygen, thus lowering the dissociation constant of the conjugate acid. Complete protonation of methoxymethoxybenzoic acids might be required because of the unstable carbonium ion intermediate. 

While the rates of alkaline and pH-independent hydrolysis of [93] and [94] are similar, hydronium ion catalysis is 2500 times less favourable in the case of the cyclic acylal. The large rate difference in comparison with the open chain analogue may reflect the fact that, if a carbonium ion intermediate with a carboxyl group held rigidly adjacent to the carbonium carbon atom were formed in an A-1 reaction, rapid reclosure of the ring would result from recapture of the carbonium carbon by the carboxyl group [equation (55)]. A greatly diminished rate of hydrolysis would result. Perhaps there is a... 

Peptide chains have a direction and therefore two different ends. The amino terminus (N terminus) of a peptide has a free ammonium group, while the carboxy terminus (C terminus) is formed by the carboxylate group of the last amino acid. In peptides and proteins, the amino acid components are usually linked in linear fashion. To express the sequence of a peptide, it is therefore suf cient to combine the three-letter or single-letter abbreviations for the amino acid residues (see p. 60). This sequence always starts at the N terminus. For... 

Oxidative ring cleavage of cyclohexanones is achieved in ethanol at a platinum anode. Cleavage of the carbon-carbonyl bond occurs and the carbonyl centee is trapped as the carboxylic acid. The radical centre formed after bond cleavage is oxidised to the carbocation. This rearranges to the most stable centre and is then trapped by the carboxyl group to form a lactone [4, 5], An identical process is... 

The coordination polymer [Zn(tmbdc)(dmso)2]-2(DMSO) (tmbdc = 2,3,5,6-tetramethyl-l,4-benzenedicarboxylate) has been synthesized by layer diffusion in DMSO (dimethyl sulfoxide) solution. The compound contains ID chain formed by octahedraly coordinated Zn ion chelated by the carboxyl groups of tmbdc. In another recently reported coordination polymer [Zn2(bdc)2(dmso)2]-5(DMSO) (bdc = 1,4-... 

In conclusion, ID coordination polymer [Zn(tmbdc)(dmso)2]-2(DMSO) 2 has been synthesized with 2,3,5,6-tetramethyl-l,4-benzenedicarboxylic acid in DMSO. The structure contains ID chains formed by octahedraly coordinated Zn ions chelated by the carboxyl groups of tmbdc, rather than the 2D (4,4) nets constructed from paddle-wheel SBU of pairs Zn ions as found in [Zn2(bdc)2(dmso)2]-5DMSO 1. Analysis of the structure reveals that the steric hindrance of die four methyl groups of tmbdc determines the coordination environments of the zinc ions and the coordination modes of the carboxyls, and thus the final structures of the coordination polymers. The result also shows that DMSO is a stronger ancillary ligand and is also easier to be included in the structures of coordination polymers, compared to DMF. DMSO can be a better solvent for the syntheses of porous coordination polymers. 

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