Side-chain alkylation

Fig. XV-16. A schematic drawing of the arrangement of polyglutamates having alkyl side chains in an LB film. The circles represent the rodlike polyglutamate backbone oriented perpendicular to the page the wiggly lines are the alkyl sidechains. (From Ref. 182.)...

A unique but widely studied polymeric LB system are the polyglutamates or hairy rod polymers. These polymers have a hydrophilic rod of helical polyglutamate with hydrophobic alkyl side chains. Their rigidity and amphiphilic-ity imparts order (lyotropic and thermotropic) in LB films and they take on a F-type stmcture such as that illustrated in Fig. XV-16 [182]. These LB films are useful for waveguides, photoresists, and chemical sensors. LB films of these polymers are very thermally stable, as was indicated by the lack of interdiffusion up to 414 K shown by neutron reflectivity of alternating hydrogenated and deuterated layers [183]. AFM measurements have shown that these films take on different stmctures if directly deposited onto silicon or onto LB films of cadmium arachidate [184]. 

The percentage of cyclohexylation is given in Fig. 1-20. (411,412). Hydrogen abstraction from the alkyl side-chain produces, in addition, secondary products resulting from the dimerization of thiazolylalkyl radicals or from their reaction with cyclohexyl radicals (Scheme 68) (411). 

The reactivity of alkylthiazoles possessing a functional group linked to the side-chain is discussed here neither in detail nor exhaustively since it is analogous to that of classical aliphatic and aromatic compounds. These reactions are essentially of a synthetic nature. In fact, the cyclization methods discussed in Chapter II lead to thiazoles possessing functional groups on the alkyl chain if the aliphatic compounds to be cyclized, carrying the substituent on what will become the alkyl side chain, are available. If this is not the case, another functional substituent can be introduced on the side-chain by cyclization and can then be converted to the desired substituent by a classical reaction. 

On the other hand an alkyl side chain on a benzene nng is oxidized on being heated with chromic acid The product is benzoic acid or a substituted derivative of benzoic acid... 

Benzene with no alkyl side chain and no benzyhc hydrogens undergoes a different reaction under these conditions Oxidation of the ring occurs to convert benzene to its epoxide... 

A primary or secondary alkyl side chain on an aromatic ring is converted to a carboxyl group by reaction with a strong oxidizing agent such as potassium permanga nate or chromic acid... 

Tocotrienols differ from tocopherols by the presence of three isolated double bonds in the branched alkyl side chain. Oxidation of tocopherol leads to ring opening and the formation of tocoquinones that show an intense red color. This species is a significant contributor to color quaUty problems in oils that have been abused. Tocopherols function as natural antioxidants (qv). An important factor in their activity is their slow reaction rate with oxygen relative to combination with other free radicals (11). 

Fig. 7. Reactions of ttiglycetides at the carbonyl ester linkage. R represents the alkyl side chain.

For monosubstituted alkylphenols, the position of the alkyl radical relative to the hydroxyl function is designated either with a numerical locant or ortho, meta, or para. The alkyl side chain typically retains a trivial name. Thus 4-(l,l,3,3-tetramethylbutyl)phenol, 4-/ f2 octylphenol, and para-tert-octy Tph.eno (PTOP) all refer to stmcture (1). 

Other apphcations of sodium bromide iaclude use ia the photographic iadustry both to make light-sensitive silver bromide [7785-23-1] emulsions and to lower the solubiUty of silver bromides during the developing process use as a wood (qv) preservative in conjunction with hydrogen peroxide (14) as a cocatalyst along with cobalt acetate [917-69-1] for the partial oxidation of alkyl side chains on polystyrene polymers (15) and as a sedative, hypnotic, and anticonvulsant. The FDA has, however, indicated that sodium bromide is ineffective as an over-the-counter sleeping aid for which it has been utilized (16). 

Physical properties, which depend on molecular weight, the nature of the alkyl group, the nature of the initiator, stereospecificity, and crystallinity, range from viscous Hquids, through sticky Hquids and mbbery soHds, to brittie soHds. Polyethers with long alkyl side chains are waxy, however, as the alkyl group in such cases dominates physical properties. 

Fig. 1. T vs 8 for poly(alkyl acrylates). = number of C atoms in alkyl side chain. To convert MPa to (cal/cm ), divide by 2.05.

Alkyl side chains in both pyrazines and quinoxalines are susceptible to halogenation by elemental halogens (28JCS1960, 68TL5931) and under radical conditions with NBS (72JOC511). Thus, bromination of 2-methylquinoxaline with bromine in the presence of sodium acetate... 

Mass spectra of the same diaziridines were reported later (74JOU1140). Whereas in longer alkyl side chains of diaziridines the typical amine degradation by n -1 carbon atoms predominates, successive elimination of NH and methyl was observed in (37a). The 1-methyl compound (37b) undergoes competitive elimination of NH and MeN. 

Thiadiazoloazines fused, 6, 711-748 alkyl side-chain activation, 6, 740 bond lengths, 6, 731 electrophilic reactions, 6, 735, 736 H NMR, 6, 731 IR spectra, 6, 732 mass spectra, 6, 732... 

Whilst increasing the length of alkyl side chain can, to some extent, depress Tg and improve low-temperature properties this is at the expense of oil resistance. On the other hand lengthening of the side chain by incorporation of an —O— or an —S— linkage could often depress Tg and reduce swelling in hydrocarbon oils. This led to the commercial development of copolymers of either ethyl or butyl acrylate with an alkoxy acrylate comprising some 20-50% of the total composition. Typical of such alkoxy compounds are methoxyethyl acrylate (1) and ethoxyethyl acrylate (11) ... 

Polymers containing long alkyl side chains, typically between 16 and 22 carbon atoms in length, have been used extensively as low adhesion backsizes for PSA tape products for many years. The general structure of such polymers is shown schematically in Fig. 8. The alkyl side chains are attached through a bridging group, R, to the polymer backbone, and the backbone may contain comonomers,... 

In 1950, Dahlquist et al. [82] reported the use of polyvinyl A -alkyl carbamates as PSA release materials. Since then, many other types of alkyl side chain polymers have been patented for use as release coatings, including copolymers based on higher alkyl acrylates or methaci ylates [83-86], polyvinyl esters of higher aliphatic fatty acids [87], higher alkyl vinyl esters or ethers and a maleic... 

Fig, 9. Polymers containing long alkyl side chains typically form alternating layered structures. 

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