Hydroxy groups, terminal

Thermoplastic polyurethane elastomers are produced from prepolymers by polycondensation (12,13). A relatively high molecular-weight polyester or polyether with terminal hydroxy groups (a polyglycol) first reacts with an excess of a diisocyanate. 

In order to obtain anionic polyoxyethylene phosphate surfactants, either the terminal hydroxy group of a polyoxyethylated hydrophobic substance is reacted with a phosphorylating agent or a phosphate ester is oxalkylated. Most often aliphatic and aliphatic-aromatic alcohols are first treated with an alkylene oxide and afterward with one of the phosphorylating agents, such as P4OI0, POCl3, phosphoric acid, or polyphosphoric acid [39-48]. 

Block copolymers were synthesized by a combination of fipase-catalyzed polymerization and atom transfer radical polymerization (ATRE). " " At first, the polymerization of 10-hydroxydecanoic acid was carried out by using lipase CA as catalyst. The terminal hydroxy group was modified by the reaction with a-bromopropionyl bromide, followed by ATRP of styrene using CuCE2,2 -bipyridine as catalyst system to give the polyester-polystyrene block copolymer. Trichloromethyl-terminated poly(e-CL), which was synthesized by lipase CA-catalyzed polymerization with 2,2,2-trichloroethanol initiator, was used as initiator for ATRP of styrene. 

Figure 5. Cartoon models of the reaction of methanol with oxygen on Cu(llO). 1 A methanol molecule arrives from the gas phase onto the surface with islands of p(2xl) CuO (the open circles represent oxygen, cross-hatched are Cu). 2,3 Methanol diffuses on the surface in a weakly bound molecular state and reacts with a terminal oxygen atom, which deprotonates the molecule in 4 to form a terminal hydroxy group and a methoxy group. Another molecule can react with this to produce water, which desorbs (5-7). Panel 8 shows decomposition of the methoxy to produce a hydrogen atom (small filled circle) and formaldehyde (large filled circle), which desorbs in panel 9. The active site lost in panel 6 is proposed to be regenerated by the diffusion of the terminal Cu atom away from the island in panel 7.

The preformed (BC) method is a one-step process used in this case to introduce high multiplicity of terminal hydroxy groups. The method involves direct coupling of branch cell reagents (i.e. tris(hydroxymethyl)aminomethane (Tris-)) by amidation of ester terminated PAMAM dendrimers. Advancement to the next generation of branch cells occurs in one step. 

Under aqueous conditions formaldehyde reacts with primary nitramines to form the corresponding methylol derivatives. The versatility of the terminal hydroxy group of these methylol derivatives is illustrated by their facile conversion to more reactive functional groups, like isocyanates, which can then be reacted with compounds containing hydroxy or carboxy functionality. Diisocyanates like (215), (216) and (217) have been reacted with various polyni-troaliphatic diols for the synthesis of energetic polymers. ... 

Diene carbanions exhibit a reactivity similar to that of styryl carbanions. Carban-ionic sites of lower reactivity can be functionalized under certain conditions32). Living polymers with alkoxide end groups exhibit the same reactivity as alcoholates with respect to proton-donating substances and activated organic halides. Protonation yields terminal hydroxy groups which are often used in the two-step macromonomer synthesis. 

Polyoxyethylene macromonomers have been synthesized on the basis of PEO chains bearing at one end a terminal hydroxy group. 

The use of 2-mercaptoethanol, HS—CH2—CH2- OH, as a transfer agent belongs to the early attempts to synthesize macromonomers by means of free-radical polymerization l0). Methyl methacrylate was employed as the monomer. The formed polymers bear a terminal hydroxy group which was subsequently reacted with methacryloyl chloride. 

When 5-amino-1-pentanol was used as an additive, amino groups reacted prior to hydroxy groups, leading to the formation of a polystyrene derivative with side-chains having terminal hydroxy groups. The hydroxy groups could be modified with MA, and polymerized with styrene to afford a network polymer again. 

Many examples of sphingolipids exist in which the C2-amino and/or terminal hydroxy group is modified. A,A/-Dimethyl-D-eryffiro-sphingosine is a naturally occurring sphingolipid that, like -sphingosine, inhibits the ubiquitous signal trans-... 

Sphingomyelin (ceramide 1-phosphorylcholine, compound 1, Fig. 3) is a phospholipid in which the terminal hydroxy group... 

The terminal hydroxy group of ceramide has also been modified. 1-0-Methoxyceramide did not inhibit mitochondrial ceramidase (69), and 1-fluoroceramide was a weak inhibitor of glucosylceramide formation in cultured murine neuronal cells (80). The 1-methylthio analog of dihydroceramide activated sphinganine kinase and dismpted neuron axonal growth in cell cultures (81). 

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