PPH

There is more to tire Wilkinson hydrogenation mechanism tlian tire cycle itself a number of species in tire cycle are drained away by reaction to fomi species outside tire cycle. Thus, for example, PPh (Ph is phenyl) drains rhodium from tire cycle and tlius it inliibits tire catalytic reaction (slows it down). However, PPh plays anotlier, essential role—it is part of tire catalytically active species and, as an electron-donor ligand, it affects tire reactivities of tire intemiediates in tire cycle in such a way tliat tliey react rapidly and lead to catalysis. Thus, tliere is a tradeoff tliat implies an optimum ratio of PPh to Rli. 

In the reaction of a substituted ylide (r CH—PPh ) with an aldehyde R CHO, a stereochemical problem arises. Much work has been carried out in order to achieve control of either cis- or rrans-alkene formation. This work has been reviewed several times with always changing viewpoints (A. Maercker, 1965 L.D. Bergelson, 1964 M. Schlosser, 1970 H. Best-mann, 1979). 

Butyl-5-methyl 2-Bromo-5-methylacetanilide l-(Tri-n-butyl-stannvl)hexyne, (1) Pd(PPh,)4, (2) PdCl lCHjCN) 81,77 [1]... 

Diethoxymethyl)- 1-methanesulfonyl 2-Iodo-iV-(methane- sulfonyl)anilinc 3,3-Diethoxy propyne Pd(PPh,),Cl Cul 63 [2]... 

Methyl-5-(4-pyridyl)-7-aza- 2-Araino-3-iodo-6-methyl-,S- (4-pyridyl)pyridine Trimethylsilylethyne. Pd(PPh,)jCl4, Cut 96,40 ... 

Raw Materials. PVC is inherently a hard and brittle material and very sensitive to heat it thus must be modified with a variety of plasticizers, stabilizers, and other processing aids to form heat-stable flexible or semiflexible products or with lesser amounts of these processing aids for the manufacture of rigid products (see Vinyl polymers, vinyl chloride polymers). Plasticizer levels used to produce the desired softness and flexibihty in a finished product vary between 25 parts per hundred (pph) parts of PVC for flooring products to about 80—100 pph for apparel products (245). Numerous plasticizers (qv) are commercially available for PVC, although dioctyl phthalate (DOP) is by far the most widely used in industrial appHcations due to its excellent properties and low cost. For example, phosphates provide improved flame resistance, adipate esters enhance low temperature flexibihty, polymeric plasticizers such as glycol adipates and azelates improve the migration resistance, and phthalate esters provide compatibiUty and flexibihty (245). 

Physical Properties. Nitrobenzene is readily soluble in most organic solvents and is completely miscible with diethyl ether and benzene. Nitrobenzene is only slightly soluble in water with a solubiUty of 0.19 parts pet 100 parts of water at 20°C and 0.8 pph at 80°C. Nitrobenzene is a good organic solvent. For example, it is used in Friedel-Crafts reactions because aluminum chloride is soluble in nitrobenzene. The physical properties of nitrobenzene are summarized in Table 1. 

Fig. 7. Influence of copper naphthenate on exotherm temperature. Composition in pph isophthalic laminating resin is cobalt naphthenate (0.20), dimethylaniline (0.05), and copper naphthenate, A (0.00) B (0.01) C (0.015) orD (0.02).

At low latex soHds-to-pulp ratios, ie, 10—20 pph, latex is added to the beaten pulp to give a paper web with superior web strength, elongation, bursting strength, internal bond, and tear strength. The nitrile latices and medium styrene—butadiene are commonly used as beater additions. In a similar manner, latex can be deposited on asbestos fibers. Such compositions are used as gaskets, linoleum bases, etc. 

At high (50—100 pph) saturation levels, with a near thermoplastic elastomer, a leather-like material results that can be embossed. The paper web used ia pressure-seasitive tape is prepared by latex saturatioa ia order to give it sufficieat internal strength to release without delamiaatioa. 

The PPhs function is converted into H during work-up. 

Bis(spiroisoxazoline) was cleaved by PPhs in PhH/MeOH to provide an oxime, and in benzene to produce an amide (75MI41609). 

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