Subject halogenating agents

An aryloxypyrimi done has been described as an anti ulcer agent this activity is of note since the agent does not bear any structural relation to better known anti ulcer drugs. Displacement of halogen on the acetal of chloro-acetaldehyde by alkoxide from m-cresol gives the intermediate This affords enaminoaldehyde when subjected... 

The hazards of all common solvents and reagents are well known and those of new materials can often be inferred from structural properties and similarities. For example, toxic effects are to be expected from certain classes of heterocycle, particularly those that are subject to easy nucleophilic replacement of halogen and therefore are alkylating agents in their effect on biomolecules. For example,the fungicide davicil (2,3,5,6-tetrachloro-4-methylsulfonylpyridine) and the useful intermediate 5-bromo-2,4-dichloropyrimidine, are allergenic substances, the latter very strongly so. 

Further subjects in the spotlight are foaming agents, notably CFCs, which are now forbidden in many countries. Other additives or processing aids under debate, such as brominated and other halogenated flame retardants, cadmium and lead heat stabilisers and release agents which cause damage to the ozone layer, are discussed in more detail in Table 3.5 of Chapter 3. 

Derivatization with halogenated compounds offers the advantage that the derivatives are subject to extremely sensitive detection with an electron capture detector (BCD). The disadvantage is that excess derivatization agent remains in the sample solution after the reaction, necessitating its removal prior to gas chromatographic determination because of the potential for interference during BCD detection. 

In adding hydrogen halides and halogens to the >C=C< double bond of 1,2-PB, the functionalization degree of the polymer is mostly determined by the reactivity of the electrophilic agent. Relatively low degree of polydiene hydrochlorination (10-15%) at interaction of HCl and syndiotactic 1,2-PB [16, 39, 40] is caused by insufficient reactivity of hydrogen chloride in the electrophilic addition reaction by the double bond (Table 3.2). Due to this, more electron-saturated >C=C< bonds in 1,4 units of butadiene polymerization are subjected to modification. 

---