Sulphate esters, hydrolysis

FGIy is the nucleophile in the first step of sulphate ester hydrolysis... 

Phosphate ester hydrolysis Sulphate ester hydrolysis... 

A s/cr.s possess a fruity smell and usually distil without decomposition. Boil with refltiK for 5 minutes on the water-btith a few c.c. of the licpiid with 3 to 4 volumes of a ten pei cent, solution of ctLListic potash in methyl alcohol and pour into water. Notice if the liquid dissolves and has lost the odour of the ester. An ester will be completely hydrolysed, and if the alcohol is soluble in water a clear solution will be obtained. If the alcohol is vol.atile and the solution neiitialised w ith sulphuric acid. and evaporated on the water-bath, the alkali salt of the organic acid mixed with pottissium sulphate will be left and the acid may be investigated as desciibed under 1. If it is required to. ascertain the nature of the alcohol in the ester, hydrolysis must fig effected with a strong aqueous solution of caustic potash... 

Isopropanol [67-63-0] M 60.1, b 82.5°, d 0.783, n25-8 1.3739. Isopropyl alcohol is prepared commercially by dissolution of propene in H2SO4, followed by hydrolysis of the sulphate ester. Major impurities are water, lower alcohols and oxidation products such as aldehydes and ketones. Purification of isopropanol follows substantially the same procedure as for n-propyl alcohol. 

Flydrolysis is an important metabolic reaction for drugs whose structures contain ester and amide groups. All types of ester and amide can be metabolized by this route. Ester hydrolysis is often catalysed by specific esterases in the liver, kidney and other tissues as well as non-specific esterases such as acetylcholinesterases and pseudocholinesterases in the plasma. Amide hydrolysis is also catalysed by non-specific esterases in the plasma as well as amidases in the liver. More specific enzyme systems are able to hydrolyse sulphate and glucur-onate conjugates as well as hydrate epoxides, glycosides and other moieties. 

The resultant sulphate ester can be converted to the alcohol by acid hydrolysis. If an acid-sensitive group is present, this hydrolysis is still successful through use of a catalytic amount of sulphuric acid in the presence of 0.5-1.0 equivalents of water with tetrahydrofuran as solvent. The use of base in the formation of the cyclic sulphates themselves can also alleviate problems associated with acid-sensitive groups [117,118]. 

The observed reactivity sequence for aliphatic sulphonates closely resembles that for the corresponding aliphatic sulphates ethylene sulphate, trimethylene sulphate and dimethyl sulphate (12 1 6)127 for which S—O bond fission (14%) was again only observed for the hydrolysis of a five-membered cyclic sulphate. The heats of hydrolysis have, however, been measured for aliphatic sulphate esters and the existence of considerable ring strain in the five-membered system is indicated by the fact that the heat of hydrolysis of ethylene sulphate exceeds that of dimethyl sulphate by 5-6kcalmol-121. 

Sulphate ester conjugates can be converted to acetyl derivatives in much the same way. This is a relatively mild procedure by which esters which are too unstable to acid hydrolysis can be characterized. The sulphate ester (10 mg) is dissolved in a 1 40 solution of methanesulphonic acid in acetic anhydride (2 ml) at 0°C and the mixture is then heated at 100 °C for 30 min. The... 

Hydrolysis of sulphate esters and glucuronides with simultaneous perfluoroacylation... 

Consider what labile groups are present which would yield extractable hydrolysis products, e.g. amide groups yielding fatty acid, or whose decomposition would prevent their determination by some other procedure, e.g. SDS/BEC titration after acid hydrolysis of sulphates, esters or amides. 

These consist of the removal of the sialic acid by acid hydrolysis, or the half sulphate ester group by treatment with methanolic hydrogen chloride. 

Intramolecular general-acid catalysis in the hydrolysis of phosphate and sulphate esters... 

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