Alkylation, degree

Typical polymeric, partially alkylated amino resins are butylated or isobutylated condensates with an average degree of polymerization between 3 and 8 and a combined formaldehyde content of 1.4-1.8 per amino group [2.147]-[2.149]. The hydroxymethyl (methylol) groups are partially alkylated (degree of alkylation 40-80%). 

Quatemized or partially quatemized derivatives of poly(4-vinylpyridine) (DP = 1,600, Mw = 168 kDa) were synthesized by the group of Izumrudov [210]. Among them, four different series were synthesized quartemized poly(4-vinylpyridine) with V-alkyl ester substituents (C -PVP, Fig. 20b), polycarboxybetaine with alkyl spacer (C -PCB, Fig. 20c), poly[(4-vinylpyridine)-co-(V-alkyl-4-vinylpyridinium)] and poly[(iV-methyl-4-vinylpyridine)-c )-(V-alkyl-4-vinylpyridinium)] both with various alkylation degree p (respectively Cn-PVP-p, Fig. 20d and Me-Cn-PVP-p, Fig. 20e). Unfortunately, relatively few comparisons between these polymers were presented in this publication regarding the physico-chemical characteristics of their polyplexes. At a charge ratio of 5, Cn-PVP-based polyplexes with short V-alkyl... 

The object of these studies has been the determination of the degree of association in thiazole and its alkyl derivatives. Various solvents have been used cyclohexane (154), carbon tetrachloride (155, 156), benzene and nitrobenzene (157). 

Carbon atoms are classified according to their degree of substitution by other car bons A primary carbon is directly attached to one other carbon Similarly a secondary carbon is directly attached to two other carbons a tertiary carbon to three and a qua ternary carbon to four Alkyl groups are designated as primary secondary or tertiary according to the degree of substitution of the carbon at the potential point of attachment... 

Alcohols and alkyl halides are classified as primary secondary or tertiary according to the degree of substitution of the carbon that bears the functional group (Section 2 13) Thus primary alcohols and primary alkyl halides are compounds of the type RCH2G (where G is the functional group) secondary alcohols and secondary alkyl halides are compounds of the type R2CHG and tertiary alcohols and tertiary alkyl halides are com pounds of the type R3CG... 

Degree of substitution (alkyl substituents stabilize a double bond)... 

The degree to which allylic radicals are stabilized by delocalization of the unpaired electron causes reactions that generate them to proceed more readily than those that give simple alkyl radicals Compare for example the bond dissociation energies of the pri mary C—H bonds of propane and propene... 

Potential energy diagram (Section 4 8) Plot of potential en ergy versus some arbitrary measure of the degree to which a reaction has proceeded (the reaction coordinate) The point of maximum potential energy is the transition state Primary alkyl group (Section 2 13) Structural unit of the type RCH2— in which the point of attachment is to a pnmary carbon... 

Rate of polymerization. The rate of polymerization for homogeneous systems closely resembles anionic polymerization. For heterogeneous systems the concentration of alkylated transition metal sites on the surface appears in the rate law. The latter depends on the particle size of the solid catalyst and may be complicated by sites of various degrees of activity. There is sometimes an inverse relationship between the degree of stereoregularity produced by a catalyst and the rate at which polymerization occurs. 

Haloall lation. Haloalkyl groups can be introduced directiy by processes similar to Friedel-Crafts alkylation into aromatic and, to some extent, ahphatic compounds. Because halo alkylations involve bi- or polyfunctional alkylating agents, they must be performed under conditions that promote the initial halo alkylation but not, to any substantial degree, subsequent further alkylations with the initially formed haloalkylated products. 

AlkyUithium compounds are primarily used as initiators for polymerizations of styrenes and dienes (52). These initiators are too reactive for alkyl methacrylates and vinylpyridines. / -ButyUithium [109-72-8] is used commercially to initiate anionic homopolymerization and copolymerization of butadiene, isoprene, and styrene with linear and branched stmctures. Because of the high degree of association (hexameric), -butyIUthium-initiated polymerizations are often effected at elevated temperatures (>50° C) to increase the rate of initiation relative to propagation and thus to obtain polymers with narrower molecular weight distributions (53). Hydrocarbon solutions of this initiator are quite stable at room temperature for extended periods of time the rate of decomposition per month is 0.06% at 20°C (39). 

AH higher a-olefins, in the presence of Ziegler-Natta catalysts, can easily copolymerise both with other a-olefins and with ethylene (51,59). In these reactions, higher a-olefins are all less reactive than ethylene and propylene (41). Their reactivities in the copolymerisation reactions depend on the sise and the branching degree of their alkyl groups (51) (see Olefin polya rs, linear low density polyethylene). 

Gas chromatography (gc) has been used extensively to analyze phenoHc resins for unreacted phenol monomer as weU as certain two- and three-ring constituents in both novolak and resole resins (61). It is also used in monitoring the production processes of the monomers, eg, when phenol is alkylated with isobutylene to produce butylphenol. Usually, the phenoHc hydroxyl must be derivatized before analysis to provide a more volatile compound. The gc analysis of complex systems, such as resoles, provides distinct resolution of over 20 one- and two-ring compounds having various degrees of methylolation. In some cases, hemiformals may be detected if they have been properly capped (53). 

Laminates. Laminate manufacture involves the impregnation of a web with a Hquid phenoHc resin in a dip-coating operation. Solvent type, resin concentration, and viscosity determine the degree of fiber penetration. The treated web is dried in an oven and the resin cures, sometimes to the B-stage (semicured). Final resin content is between 30 and 70%. The dry sheet is cut and stacked, ready for lamination. In the curing step, multilayers of laminate are stacked or laid up in a press and cured at 150—175°C for several hours. The resins are generally low molecular weight resoles, which have been neutralized with the salt removed. Common carrier solvents for the varnish include acetone, alcohol, and toluene. Alkylated phenols such as cresols improve flexibiUty and moisture resistance in the fused products. 

Carbon Cha.in Backbone Polymers. These polymers may be represented by (4) and considered derivatives of polyethylene, where n is the degree of polymeriza tion and R is (an alkyl group or) a functional group hydrogen (polyethylene), methyl (polypropylene), carboxyl (poly(acryhc acid)), chlorine (poly(vinyl chloride)), phenyl (polystyrene) hydroxyl (poly(vinyl alcohol)), ester (poly(vinyl acetate)), nitrile (polyacrylonitrile), vinyl (polybutadiene), etc. The functional groups and the molecular weight of the polymers, control thek properties which vary in hydrophobicity, solubiUty characteristics, glass-transition temperature, and crystallinity. 

Paraffin alkylation as discussed here refers to the addition reaction of an isoparaffin and an olefin. The desired product is a higher molecular weight paraffin that exhibits a greater degree of branching than either of the reactants. 

Determining the degree of substitution using standard proton nmr refles on the integral ratio between the ceUulosic ring protons ( i 5.0-2.96) and the ester alkyl protons ( i 1.26 for butyryl and propionyl and i 2.06 for acetyl methyl groups). This simple procedure is used extensively to determine the extent of esterification and is currently the fastest, easiest way for determining the DS of mixed cellulose esters. 

Inductive and resonance stabilization of carbanions derived by proton abstraction from alkyl substituents a to the ring nitrogen in pyrazines and quinoxalines confers a degree of stability on these species comparable with that observed with enolate anions. The resultant carbanions undergo typical condensation reactions with a variety of electrophilic reagents such as aldehydes, ketones, nitriles, diazonium salts, etc., which makes them of considerable preparative importance. 

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