FAR, replacement of hydroxyl

Replacement of hydroxyl by fluorine converts perfluoroalkanecarboxylic acids toperfluoroalkanoylfluorides The short chain acids react exothermally with FAR added in a dropwise manner, whereas the longer chain acids require heating [78] (equation 49) Attempts to fluorinate pentafluorobenzoic acid with FAR leads to decarboxylation to give pentafluorobenzene [78]... 

Hydrolysis usually refers to the replacement of a sulfonic group (-S03H) or a chloro group (-C1) with an hydroxyl group (-OH) and is usually accomplished by fusion with alkali. Hydrolysis uses a far wider range of reagents and operating conditions than most chemical conversion processes. 

In all of the examples so far described (except the isomerization), the oxirane ring is formed by way of internal, bimolecular replacement of the sulfonyloxy group by an alkoxide ion resulting from the neighboring hydroxyl group under alkaline conditions (see Scheme 10). An energetically advantageous situation for the transition state... 

In the previous chapters the preparation and properties of certain important classes of compounds have been discussed, and the principles which are illustrated in their transformations into one another have been emphasized. These principles are of wide application and can be employed in the preparation of compounds of more complex structure than any met with so far. For example, the method of preparing an alcohol by the treatment of an alkyl halide with water or an alkali, is very general in its application. The reaction consists in the replacement of a halogen atom by a hydroxyl group, and such replacement takes place not only with alkyl halides, but with other compounds which contain halogen. Thus, chloroacetic acid can be transformed into hydroxyacetic acid by water —... 

The replacement of carbon by phosphorus has a number of important consequences (a) an additional substituent group is present in the molecule (hydroxyl), (b) the central atom (phosphorus) has a tetrahedral configuration, whereas the carbonyl atom is planar, (c) there are significant differences in steric bulk and in acidity (pK, ). The tetrahedral configuration of phosphorus has important implications in the design of transition state-analogue enzyme inhibitors, which have a far-reaching potential in medicinal chemistry. 

The recurring theme in work on corticoids discussed thus far with the exception of the 17-desoxy compounds consisted in the introduction of additional functions to the basic cortisone molecule. Some further success in producing biologically active molecules has been achieved by substituting unnatural functions for those present in the protoype molecule. Thus the hydroxyl groups at both C-ll and C-21 can be replaced by halogen with retention of activity. 

An intense band due to the bulk hydroxyl stretch is observed at 3140 cm . Two far less intense bands at 3660 and 3484 cm can be attributed to the surface hydroxyl groups. In general, these bands can only be detected on an evacuated surface. The most reasonable assignment for these bands appears to be that of Russell et al. (1974) who found that the band at 3660 cm disappeared completely when the surface was phosphated and so attributed it to the singly coordinated OH groups the band at 3484 cm was not replaceable by adsorbed phosphate and was considered to consist of contributions from the doubly and triply coordinated OH groups. 

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