Functional groups hydroxyl

Both pigmented and unpigmented polyurethane paints have been prepared using a polyester resin containing hydroxyl functional groups and the biuret trlmer of hexamethylenedllsocyanate as a crosslinker. The molar ratio of hydroxyl/isocyanate has been chosen 1.0 and the pig-ment/binder ratio 0.6. 

The anti-Markovnikov product was formed with >95% regioselectivity at 35°C. The examples in Scheme 5-21, Eq. (1) show that cyano and hydroxyl functional groups are tolerated by the catalyst, and diphenylphosphine oxide can be added to both C=C bonds in a di-alkyne. The reaction also worked for internal alkynes (Scheme 5-21, Eq. 2). Unusual Markovnikov selectivity was observed, however, for 1-ethynyl-cyclohexene (Scheme 5-21, Eq. 3) [17]. 

If the carboxylic acid has two carboxyl functional groups (a dicarboxylic acid) and if the alcohol has two hydroxyl functional groups (a diol), a polyester will result nHOOC—R—COOH + nHO—R —OH —> +OOC—R—COO—R +n + nH20. 

The reactions of the six-membered chlorocyclophosphazene were studied with a number of aliphatic diamines (169 175), aromatic diamines (176), aliphatic diols (177-179), aromatic diols (180,181) and compounds containing amino and hydroxyl functional groups (169,170,182). This subject has been reviewed (11,16,20). There are at least five different reaction products that are possible (Fig. 19). Replacement of two chlorine atoms from the same phosphorus atom produces a spirocyclic product. Replacement of two chlorine atoms from two different phosphorus atoms in the same molecule produces an ansa product. Reaction of only one end of the difunctional reagent, resulting in the substitution of only one chlorine atom, leads to an open-chain compound. Intermolecular bridged compounds are formed when the difunc-... 

An alpha hydroxy acid is an organic carboxylic acid in which an additional hydroxyl functional group (-OH) is present at the alpha position, i.e., on the carbon adjacent to the carboxyl functionality, -COOH. Figure 13.10.1 presents the struc-... 

Figure 9.38 The acetyl azide group of this Cascade Blue derivative has dual functions. It can react with amine groups to form amide bonds, or it can be converted to an isocyanate at high temperatures to couple with hydroxyl functional groups, creating a carbamate linkage.

The hydroxylic content of the dextran sugar backbone makes the polymer very hydrophilic and easily modified for coupling to other molecules. Unlike PEG, discussed previously, which has modifiable groups only at the ends of each linear polymer, the hydroxyl functional groups of dextran are present on each monomer in the chain. The monomers contain at least 3 hydroxyls (4 on the terminal units) that may undergo derivatization reactions. This multivalent nature of dextran allows molecules to be attached at numerous sites along the polymer chain. 

Only three amino acids have a hydroxyl functional group in their side chain tyrosine, serine and threonine. Some kinases target only tyrosine residues (tyrosine kinases) whereas others may phosphorylate serine or threonine (Ser/Thr kinases). An enzyme protein (the substrate for the kinase) may have several tyrosine, serine or threonine residues within its primary sequence, but only some of these are subject to phosphorylation by a particular kinase (see Figure 3.6)... 

The organic fraction composition may influence the exchange capacity. A key contribution to the exchange capacity of humus is given by the carboxyl and phenolic hydroxyl functional groups. Under appropriate pH conditions, uranic acids in polysaccharides or carboxy-terminal structures in peptides can contribute to the... 

Alcohols, which contain a hydroxyl functional group, can undergo dehydration reactions with either carboxylic or phosphoric acid to form esters. The double arrows used in this and subsequent equations indicate that the reaction can go in either direction. 

---