2- ethyl carbonate cleavage

Cleavage of aryl carbonates (general procedure)To a solution of NaHTe prepared in situ from tellurium powder (1.3 g) and NaBH4 (0.9 g) in EtOH (20 mL) bnffered with deoxygenated HO Ac (1.2 mL in 5 mL EtOH) is added the aryl ethyl carbonate (5 mmol) and the mixture refluxed under N2 for 30 min. The reaction mixture is filtered, the filtrate evaporated and the residue dissolved in H2O. The aqueous layer is slightly acidified with a few drops of HOAc. The respective phenols are obtained in quantitative yields. 

Under alkaline conditions isolating lignin degradation products which are essentially of a phenyl.ethyl rather than a phenylpropyl nature is structurally important and requires a lignin structure by which the 7-carbon may be removed as a result of a 0-7 carbon-carbon cleavage reaction, either by direct alkaline hydrolysis or alkali-catalyzed hydrogenolysis. 

Cleavage of the carbon-carbon bond in ethane yields two methyl radicals whereas propane yields an ethyl radical and one methyl radical Ethyl radical is more stable than methyl and so less energy is required to break the carbon-carbon bond in propane than in ethane The measured carbon-carbon bond dissociation energy in ethane is 368 kJ/mol (88 kcal/mol) and that in propane is 355 kJ/mol (85 kcal/mol)... 

Nitrophenyl)ethyl Carbamate. The photolytic removal of this group occurs twice as fast as does the 2-nitrobenzyl carbamate. Additionally, substitution at the alpha carbon increases the rate of cleavage even more. 

Selective ether cleavage comes about during the substitution step, which obeys an Sn2 mechanism. Therefore, selective cleavage requires selective attack by Y on one of the electrophilic carbons in the protonated ether. Determine if selective attack is likely by examining the shape of the lowest-unoccupied molecular orbital (LUMO) in protonated ethyl propyl ether. Is this orbital larger near one carbon than the other If so, what product combination will result What other atom(s) contribute to the LUMO What would happen if 1 attacked this atom(s) ... 

The reaction of carbon oxysulphide with a-aminonitriles results in 5-amino-2-hydroxy thiazoles these are structurally similar to the 2-mercaptothiazoles but are found to be less stable, readily undergoing cleavage or rearrangement to give 4-thiohydantoins. Thus the reaction between ethyl aminocyanoacetate and carbon oxysulphide 31 in ether afforded 5-amino-2-hydroxy-4-carbethoxythiazole 32, which in the presence of aqueous ammonia was converted into 5-carbethoxy-4-thiohydantoin 33. When using sodium... 

Dopamine, a neurotransmitter, was covalently coupled, via an amide bond, to a modified polystyrene having A-(2-(3,4-dihydroxyphenyl)ethyl) isonicotinamide units. The dopamine-coupled polymer was coated onto glassy carbon electrodes. In aqueous electrolyte solutions (pH 7), cathodic current caused cleavage of the amide linkage and release of dopamine at potentials more negative than 0.9 V [41]. The chemical scheme for the amide bond cleavage is presented in Figure 18. 

Mechanisms involving axial coordination of the optically active amine have also been invoked, and crystal structure data on RCo(DMG)2B complexes, where R is alkyl or (R)-l-(methoxycarbonyl)ethyl, and B is (R )-a-methylbenzylamine, were obtained (316, 317). Because deuteration of the (R)-methoxycarbonyl complex gave (5)-methylpropionate-2-d, it was concluded that Co—C bond cleavage occurred with inversion of configuration at the carbon (317). It would be useful to know the mechanistic details of this step, which could involve attack by D+, DCo(III), or coordinated D, as well as D2, for it is an unusual, if not unique, observation [contrast with the usual retention mechanism outlined in Eq. (39)]. 

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