Nitrile groups, pendant

Addition of acrylonitrile to cyclic amines yields the per-7V-(2-cyanoethyl)-substituted macrocycles,124 which can be reduced to form the 2-aminopropyl compounds,125 or hydrolyzed to form the 2-carbamoylethyl compounds.126 Pendant nitrile groups coordinate only weakly. 

A detailed study of hydrogenation of several alkenes and polybutadiene was undertaken using the catalysts [RhCl(HEXNa)2]2 and [RhCl(OCTNa)2]2 (HEXNa and OCTNa, Structures 8 and 9) [52] with or without an added solvent (toluene). With both catalysts the terminal alkenes were hydrogenated much faster than the internal ones, and this was also reflected in the preferential hydrogenation of the pendant vinyl units (products of 1,2-addition) in polybutadiene versus the internal double bonds (from 1,4-polymerization) (Eq. 31). Internal double bonds in 2-pen-tene- and 3-pentenenitriles were hydrogenated unusually fast compared with simple alkenes such as 1-octene, with no concomitant reduction of the nitrile group. 

Toluene is also adsorbed on the palladium surface in a flat orientation, whereas benzonitrile is adsorbed pendant with the nitrile group interacting with the sur-... 

Polyacrylonitrile (PAN) has pendant nitrile groups and therefore was selected as a prime candidate for modification by organotitanium complexes, PAN also can be easily fabricated into fibers and processed at elevated temperatures to produce "carbon" which can simultaneously undergo a "solid state" reaction with titanium. Under appropriate processing conditions it was envisaged that Ti-C would be the main constituent of the end product. 

A. Banihashemi and B. Akhlaghinia. Synthesis and crosslinking of poly(ether-ketone)s, and poly(ether-ketone-sulphone)s with pendant nitrile groups (II). Iranian Polym. J., 11 365-371,2002. 

The third type of monomer pair is that which shows an alternating tendency. This tendency is related to the polarization properties of the monomer substituents [73]. Monomers that are dissimilar in polarity tend to form alternating monomer sequences in the polymer chain. An example is the monomer pair acrylonitrile-styrene, with Ri = 0.07 and i 2 = 0-37, with corresponding component rate constants shown in Table 12.7. Styrene, with its pendant phenyl group, has a relatively electronegative double bond, while acrylonitrile, with its electron-withdrawing nitrile group, tends to be electropositive. 

Other authors such as Berlin et al (1964) [152] and Fester (1965) [154,161] have discussed the formation of the chromophore, also with the elimination of hydrogen, but with the formation of a polyene structure, (Scheme VII) (a conjugated double bond structure with a pendant nitrile group). 

The piezoelectricity in amorphous polymers differs from that in semi-crystalline polymers and inorganic crystals in that the polarization is not in a state of thermal equilibrium, but rather a quasi-stable state due to the ffeezing-in of molecular dipoles. As mentioned by Broadhurst and Davis (55), four criteria are essential to make an amorphous polymer exhibit piezoelectric behavior. First, molecular dipoles must be present. As seen in Table 1, these dipoles are typically pendant to the polymer backbone as are the nitrile groups in PAN, PVDCN-VAC, and (p-CN) APB/ODPA. However, the dipoles may also reside within the main chain of the polymer such as the anhydride units in the (P-CN) APB/ODPA polyimide. In addition to a dipole moment X, the dipole concentration N (number of dipoles per unit volume) is also important in determining the ultimate polarization, P , of a polymer. 

For copolymers of butadiene and acrylonitrile, cyclisation will be more facile due to the pendant nitrile group as in the case with polyacrylonitrile polymers [65,55]. This mechanism of decomposition suggests that the greater the alternating nature of the polymers, the greater will be the extent of cyclisation reactions. The cyclised polymers would undergo further thermal degradation to produce various products. 

Instead, Marien proposes that linear polyimines form from pendant nitrile groups on neighboring diains which subsequently form intensdy colored nitrones upon oxidation. He believes that dienophiles can intercept the polyimine intermediate and disrupt its conjugation (Scheme 8X However, tlK use of dienophiles to control discoloration is inefficient because the discoloration that does take place is not reversed by the addition of more dienophile. Apparently once the conjugated polyimine becomes oxidized to the nitrone, it becomes deactivated as a Diels-Alder diene. A finding that tends to support the interchain reaction of nitriles is that the solubility of SAN decreases during heating [87]. 

Infrared spectra of the zeolite/polymer inclusions and of PAN extracted from the zeolites show also peaks characteristic of the bulk polymer,including methylenic C-H stretching vibrations of the backbone (2940 cm l and at 2869 cm"l), and a band at 2240 cm l due to the pendant nitrile group. The spectra of the extracted intrazeolite polymers are indistinguishable from the spectrum of the bulk polymer. We conclude that the polymer formed in the zeolites is polyacrylonitrile. 

Cheng and Foxman 2 studied the polymerization of the square-planar nickel(II) complex, [NiBr2 P(C2H4CN)3)2]. This compound has pendant nitrile groups and the nickel ion has the potential to increase its coordination number by two. Accordingly, a thermal polymerization occurs in the solid state with formation of a blue polymeric product. Scheme 12.8. 

T he free radical initiated polymerization of polar monomers containing pendant nitrile and carbonyl groups—e.g., acrylonitrile and methyl methacrylate—in the presence of metal halides such as zinc chloride and aluminum chloride, is characterized by increased rates of polymerization (2, 3, 4, 5,10, 30, 31, 32, 33, 34, 53, 55, 65, 66, 75, 76, 77, 87). Imoto and Otsu (30, 33, 34) have attributed this effect to the formation of a complex between the polar group and the metal halide. The enhanced reactivity of the complexed monomer extends to copolymerization with uncomplexed monomers, such as vinylidene chloride, which are readily responsive to... 

The Kametani group has made considerable use of the intramolecular trapping of benzynes by pendant carbanion centers. The nitrile (133) is a key and versatile intermediate in many of the K etani studies, including the preparation of optically pure estradiol. The ester of the benzocyclobutenecarboxylic acid (134) was prepared by a similar benzyne cyclization. The acid (134) was converted via oxidative decarboxylation and HCl hydrolysis to the very labile tra/t5-2-arylbenzocyclobutenol (135), which was used in the preparation of p ophyllotoxin. ... 

---