Polymerized alcohols

Many of these reactions are reversible, and for the stronger nucleophiles they usually proceed the fastest. Typical examples are the addition of ammonia, amines, phosphines, and bisulfite. Alkaline conditions permit the addition of mercaptans, sulfides, ketones, nitroalkanes, and alcohols to acrylamide. Good examples of alcohol reactions are those involving polymeric alcohols such as poly(vinyl alcohol), cellulose, and starch. The alkaline conditions employed with these reactions result in partial hydrolysis of the amide, yielding mixed carbamojdethyl and carboxyethyl products. 

Hydroboration of a,C0-dienes with monoalkylboranes gives reactive organoboron polymers which can be transformed into polymeric alcohols or polyketones by carbonylation, cyanidation, or the DOME reaction followed by oxidation (446—448). 

Polymerized Alcohols. Polyhydric alcohols (qv) such as pentaerythritol, sorbitol and glycerin can be used as the polyol component of polyethers (qv) which are used as expl and propint binders. Polyoxypropylene derivs of sorbitol have been employed extensively as components of polyurethane resins (qv), also employed as a propint binder... 

The small molecules used as the basic building blocks for these large molecules are known as monomers. For example the commercially important material poly(vinyl chloride) is made from the monomer vinyl chloride. The repeat unit in the polymer usually corresponds to the monomer from which the polymer was made. There are exceptions to this, though. Poly(vinyl alcohol) is formally considered to be made up of vinyl alcohol (CH2CHOH) repeat units but there is, in fact, no such monomer as vinyl alcohol. The appropriate molecular unit exists in the alternative tautomeric form, ethanal CH3CHO. To make this polymer, it is necessary first to prepare poly(vinyl ethanoate) from the monomer vinyl ethanoate, and then to hydrolyse the product to yield the polymeric alcohol. 

Both polyalkylene glycols [45] and side chain polymeric alcohols such as polyvinyl alcohol have been suggested. These substances are comparatively environmentally safe [1420,1553]. 

The effects of exchange depends on the relative acidities of the alcohol (or other protonic substance) and the polymeric alcohol. The exchange reaction occurs throughout the course of the polymerization if the acidities of the two alcohols are approximately the same. The polymerization rate is unaffected while the molecular weight decreases (Eq. 7-15), but the molecular weight distribution (MWD) is Poisson. 

If the added alcohol ROH is much more acidic than the polymeric alcohol, most of it will undergo reaction with the first-formed propagating species before polymerization begins. 

Reinitiation by RO Na+ would usually be slower, since ROH is relatively acidic. This results in a decreased polymerization rate and a broadening of the polymer molecular weight. The rate of polymerization will be relatively unaffected during most of the polymerization for the case in which ROH is less acidic than the polymeric alcohol. Exchange will occur in the later stages of reaction with a broadening of the MWD. 

The use of protonic compounds such as HC1 or RCOOH in place of ROH or H20 yields a different result in most systems. When such substances take part in the exchange reaction, the result is not exchange as described above but inhibition or retardation since an anion, such as Cl or RCOO, possesses little or no nucleophilicity. Reinitiation does not occur or is very slow. The polymeric alcohols are no longer dormant but are dead. Both the polymerization rate and polymer molecular weight decrease along with a broadening of the polymer... 

Ally I Type Alcohol, Polymerized. See under Polymerized Alcohols... 

Amines can be linked to polymeric alcohols as carbamates. Carbamate attachment of amines can be achieved by reaction of isocyanates with alcohol linkers, or by treatment of alcohol linkers with phosgene [339,427,428] or a synthetic equivalent thereof, followed by exposure to the amine (Figure 3.26). The reagents most commonly used for the activation of alcohol linkers are 4-nitrophenyl chloroformate [69,429-436] and carbonyl diimidazole [427,437-440], The preparation of support-bound carbamates is discussed in Section 14.6. 

Figure 3.26. Carbamate attachment of amines to polymeric alcohols. X, Y leaving groups.

Standard solid-phase peptide synthesis requires the first (C-terminal) amino acid to be esterified with a polymeric alcohol. Partial racemization can occur during the esterification of N-protected amino acids with Wang resin or hydroxymethyl polystyrene [200,201]. /V-Fmoc amino acids are particularly problematic because the bases required to catalyze the acylation of alcohols can also lead to deprotection. A comparative study of various esterification methods for the attachment of Fmoc amino acids to Wang resin [202] showed that the highest loadings with minimal racemization can be achieved under Mitsunobu conditions or by activation with 2,6-dichloroben-zoyl chloride (Experimental Procedure 13.5). iV-Fmoc amino acid fluorides in the presence of DMAP also proved suitable for the racemization-free esterification of Wang resin (Entry 1, Table 13.13). The most extensive racemization was observed when DMF or THF was used as solvent, whereas little or no racemization occurred in toluene or DCM [203]. 

As alternatives to 4-nitrophenyl chloroformate, carbonyl diimidazole [100-102] or di-A-succinimidyl carbonate [103,104] can be used to convert polymeric alcohols into alkoxycarbonylating reagents suitable for the preparation of support-bound carbamates. Polystyrene-bound alkoxycarbonyl imidazole is less reactive than the corresponding 4-nitrophenyl carbonate, and sometimes requires heating to undergo reaction with amines. Additional activation of these imidazolides can be achieved by N-methylation (Entry 9, Table 14.7). 

The properties of different samples of Al(OEt)3 differ so greatly that they were considered in the literature as different forms —polymeric ("alcohol... 

Allyl Type Alcohols, Polymerized. See under Polymerized Alcohols Aliyiene(Propyne or Propine), CH3. C CH, mw 40.06- Gas, mp -102.7°, bp -23.2° SI sol in w, sol in ale eth. Its toxicity and fire Si expln hazards are discussed in Ref 3 It was reported that an expln occurred when an attempt was made to carry out the reaction HC C. CH2C1 + 2NH3 = NH4C1 +... 

Polyglycol mono oleate Polyhydrocarboxylic acid salt Polymeric alcohol blend Polymeric blend Polymethyl naphthalene sulphonate sodium salt Polyolefin... 

Polyitaconic add is converted completdy to the methyl ester with diazomethane (7), while Fisher esterification results in partial esterification of both itaconic acid homo- and copolymers (6). DMI homopolymers and its copolymer with butadiene can be reduced with lithium aluminum hydride to the polymeric alcohols, which on the basis of solubility, may under some conditions be partially cross-linked by intermolecular ester formation (6). Hydrazine converts polydimethyl itaccmate to the polymeric dihydrazide which is water-soluble and exhibits reducing properties. The hydrazide can be treated with aldehyde or ketones to form polymeric hydrazones (45). A cross-linked polymer of bi chloroethyl ita-conate) on treatment with trietlylamine, has been converted by partial quatemization to an anion exchange resin (46). 

Several different kinds of polyurethanes are produced, depending on the nature of the polymeric alcohol used. One major use of polyurethane is in the stretchable spandex fibers used for bathing suits and leotards. These polyurethanes have a fairly low degree of cross-linking so that the resultant polymer is soft and elastic. A second major use of polyurethanes is in the foams used for insulation. Foaming occurs when a small amount of water is added during polymerization, giving a carbamic acid intermediate that spontaneously loses bubbles of COj. 

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