OH group

Typical of this type of photo-cross-linking is the case of poly(4-hydroxystyrene) (see Chart 7.10) [34]. 

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Mordant acid dyes combine simultaneously with the mordanting agent (generally Cr(OH)j) and the fibre the dyestuff generally contains ortho OH -azo or OH-OH groups. 

Carbon atom 1 in this formula is asymmetric and two stereoisomers therefore exist, depending on whether the OH group is written below (a) or above ( ) the plane of carbon atoms. Both forms crystallize either as the monohydrate or anhydrous. 

OH groups are in the para or 1,4 position to each other. This use of the prefix is confined to disubstituted benzene derivatives in such cases as para-hydrogen and paraldehyde the prefix has no uniform structural significance and is always written in full. 

There is, of course, a mass of rather direct evidence on orientation at the liquid-vapor interface, much of which is at least implicit in this chapter and in Chapter IV. The methods of statistical mechanics are applicable to the calculation of surface orientation of assymmetric molecules, usually by introducing an angular dependence to the inter-molecular potential function (see Refs. 67, 68, 77 as examples). Widom has applied a mean-held approximation to a lattice model to predict the tendency of AB molecules to adsorb and orient perpendicular to the interface between phases of AA and BB [78]. In the case of water, a molecular dynamics calculation concluded that the surface dipole density corresponded to a tendency for surface-OH groups to point toward the vapor phase [79]. 

Van Oss and Good [148] have compared solubilities and interfacial tensions for a series of alcohols and their corresponding hydrocarbons to determine the free energy of hydration of the hydroxyl group they find -14 kJ/mol per —OH group. 

Note that in the compound (CH3)2Si(OH)2 the silicon atom can hold two OH groups, unlike carbon. It is this property that makes the existence of silicones possible. By variation of the compounds and conditions of hydrolysis, straight chains, rings and cross-linked polymers are obtained, for example ... 

The replacement of the —OH group by a chlorine atom (reaction 9.4) is a very general reaction of phosphorus pentachloride. For example, if concentrated sulphuric acid is written as (H0)2S02 then its reaction with phosphorus pentachloride may be written ... 

Many phenomena ask for local, site-specific properties of a molecule such as the partial charge on a specific atom in a molecule or the hydrogen bond donor ability of a certain OH group. It would be highly desirable to have methods as simple as an additivity model to estimate such site-specific molecular properties. 

As a guide to the probable occurrence of a constant-boiling mixture, it should be noted that such mixtures most frequently occur when one of the components contains an hydroxyl (— OH) group. Only aqueous and alcoholic mixtures therefore are likely to have a constant boiling-point. 

Ethanol, being a t> pical primary alcohol containing the -CH OH group, gives on oxidation first acetaldehyde and then acetic acid. This process, when carried out by an aqueous oxidising agent, probably consists in the direct... 

Reactions of Aspirin, (i) Distinction from Salicylic acid. Shake up with water in two clean test-tubes a few crystals of a) salicylic acid, (0) aspirin, a very dilute aqueous solution of each substance being thus obtained. Note that the addition of i drop of ferric chloride solution to (a) gives an immediate purple coloration, due to the free —OH group, whereas (b) gives no coloration if the aspirin is pure. 

Alcohols containing the CH3CH(OH) group give the iodoform... 

This method of sulphonamide Tormation may obviously be invalidated by the presence of nuclear —NHj or —OH groups, which could react with ihe phosphorus pentachloride or with the subsequent —SO Cl group. 

Diasterocontrolled hydrogenation of allylic alcohols directed by the -OH group... 

A guide we can sometimes use, particularly if we use discormection b in frame 69, is to put the OH group at a branch point in the molecule, knowing that disconnection will be easy there. Try this ... 

The obvious ones are a carbonyl group next to the anion and an OH group (which can easily be converted into a leaving group) for the cation giving two possibilities ... 

With Phenylpropanolamine at hand (or ephedrine and pseudo-ephedrine) one would next need to reduce that alpha carbon OH group to get the final amine. Strike understands that the current favorite methods for doing this involve lithium and amine. HI and red P or other iodine related protocols. So when you meth heads ruin every aspect of those methods as well, what will you do then The following are a couple of OH reduction methods (Strike thinks) that have applicable use [99-100]. 

This is a nifty little way to turn catechol or guaiacol into protocate-chualdehyde or vanillin using what is called the Riemer-Tiemann reaction [137 p824, 138], It is a really ancient reaction and only works on benzene molecules that have an OH group. One needs to use KOH instead of NaOH because it is better at promoting para substitutions (don t ask). And if one is going to make vanillin from guaiacol then there needs to be a little ethanol in the reaction as well. 

If the three esterifiable OH groups of phosphoric acid have to be esterified successively with different alcohols, they have to be protected. 

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