Pentenenitrile

The first HCN addition (eq. 3) occurs at practical rates above 70°C under sufficient pressure to keep butadiene condensed in solution and produces the 1,4- and 1,2-addition products (3-pentenenitrile [4635-87-4] 3PN, and 2-meth5i-3-butenenitrile [16529-56-9] 2M3BN) in a 2 to 1 ratio. Fortunately, thermodynamics favors 3PN (about 20 1) and 2M3BN may be isomerized to 3PN (eq. 4) in the presence of a nickel catalyst. 

Pentenenitnles are produced as intermediates and by-products in DuPont s adiponitrile process. 3-Pentenenitrile [4635-87-4] is the principal product isolated from the isomerisation of 2-methyl-3-butenenitrile (see eq. 4). It is entirely used to make adiponitrile. i7j -2-Pentenenitrile [25899-50-7] is a by-product isolated from the second hydrocyanation step. Some physical properties are Hsted in Table 13. 

Uses. 3-Pentenenitrile, 3PN, is used entirely by the manufacturers to make adiponitrile. i7j -2-Pentenenitrile, 2PN, can be cycli2ed catalyticaHy at high temperature to produce pyndine, a solvent and agncultural chemical intermediate. 2PN is also chlorinated to manufacture pentachloropyndine, an intermediate in the insecticide Dursban produced by Dow. Addition of ammonia to 2PN foUowed by reduction leads to 1,3-pentadiamine (Dytek ep), which is used as a curing agent for epoxy coatings and as a chain modifier in polyurethanes. 

There are three commercial routes to ADN in use. The first method, direct hydrocyanation of 1,3-butadiene [106-99-0] has replaced an older process, cyanation via reaction of sodium cyanide with 1,4-dichlorobutane [110-56-5] owing to the lower cost and fewer waste products of the new process. During the initial steps of the direct hydrocyanation process, a mixture of two isomers is generated, but the branched isomer is readily converted to the linear 3-pentenenitrile [4635-87-4]. 

To 5.4 mmol of LDA, prepared in 25 mL of diethyl ether from diisopropylamine and 2 M butyllithium in hexane, are added 847 mg (5.00 mmol) of 2-(trimethylsilyloxy)-3-pentenenitrile in 10 mL of diethyl ether at — 78 "C. After stirring for 45 min, 671 mg (5.00 mmol) of 2-phenylpropanal, dissolved in 10 mL of diethyl ether are added. After stirring for 2 h at — 78 X, 1.20 g (10.5 mmol) of trifluoroacetie acid are added carefully to the mixture at below —70CC. 15 mL of sat. aq NH4C1 and then diethyl ether are added and the reaction mixture is allowed to reach r.t. The phases are separated and extracted with aq NH,CI and... 

Hydrocyanation of olefins and dienes is an extremely important reaction [32] (about 75 % of the world s adiponitrile production is based on the hydrocyanation of 1,3-butediene). Not surprisingly, already one of the first Rhone Poluenc patents on the use of water soluble complexes of TPPTS described the Ni-catalyzed hydration of butadiene and 3-pentenenitrile (Scheme 9.10). The aqueous phase with the catalyst could be recycled, however the reaction was found not sufficiently selective. 

The problem of terminal addition (anti-Markovnikov) of HCN to isolated unactivated double bonds was not solved until carbon monoxide-free, low-valent transition metal complexes became available. During the mid 1960s, W. C. Drinkard allowed 1-hexene to react with HCN in the presence of tetrakis(triethylphosphite)nickel(0) and the resulting product mixture contained a small amount of the terminal addition product n-heptanenitrile, and Drinkard and Lindsey found that the reaction with 3-pentenenitrile produced ADN (7). 

The current hydrocyanation process can be broken down into two major steps. In the first, HCN is added to butadiene in the presence of an NiL4 catalyst to give 3-pentenenitrile (3PN) and 2-methyl-3-butenenitrile (2M3BN) [Eq. (7)]. Fortunately the branched 2M3BN may be isomerized to the linear 3PN isomer [Eq. (8)]. In the second step, a Lewis acid promoter is added to the NiL4 (L = a phosphorus ligand) catalyst to effect the double bond isomerization of 3PN to 4-pentenenitrile (4PN) concurrently with the... 

Shipping and Storage. The DOT shipping name for 2[3]-pentenenitrile is "Toxic liquid, Flammable, Organic, N. O. S. (2[3]-Pentenenitrile)" and is in the hazard class 6.1, packing group II, UN 2929. It requires a "POISON, FLAMMABLE" label. Carbon-steel drums and tanks may be used for... 

McKinney, R.J. (1985) Kinetic control in catalytic olefin isomerization. An explanation for the apparent contra-thermodynamic isomerization of 3-pentenenitrile. Organometallics, 4, 1142. 

In asymmetric hydrocyanation reactions the desired isomers are the chiral branched products only. Good regioselectivity toward the branched product (>98%) is limited to vinylarenes. Hydrocyanation of 1,3-dienes gives a variety of mixtures depending on the catalyst and conditions 1-alkenes give the linear nitrile as major product [34]. Both are seen in the adiponitrile process in which the unwanted branched 2M3BN (hydrocyanation product from 1,3-butadiene) is isomerized to the linear product 3-pentenenitrile, which is then hydrocyanated by in-situ isomerization to 4-pentenenitrile, resulting in the linear adiponitrile. Thus vinylarenes and cyclic alkenes (mainly norbomene) are usually the substrates of choice for the asymmetric hydrocyanation. Hopefully 1,3-dienes will become feasible substrates in the near future. 

Equation 24 describes the Ni(0)-catalyzed addition of HCN to butadiene, which leads to 3-pentenenitrile together with its allylic isomer 2-methyl-3-butenenitrile (1.5 1 molar ratio). The branched allylic isomer, however, progressively isomerizes to the linear 3-pentenenitrile. 

Double-bond isomerization of 3-pentenenitrile (Equation 25) gives an equilibrium mixture containing only ca.1% of 4-pentenenitrile with respect to the 3-isomer. This isomerization occurs much faster than that leading to the thermodynamically favoured 2-pentenenitrile. 4-Pentenenitrile is preferentially hydrocyanated to adiponitrile because it reacts faster than the 3-isomer for steric reasons (Equation 26). In addition to adiponitrile, the final reaction mixture contains 2-methylglutaronitrile (from hydrocyanation of 2-methyl-3-butenenitrile), ethylsuccinonitrile (from cyanation of 3-pentenenitrile before isomerization) and 2-pentenenitrile (from isomerization of 3-pentenenitrile, which does not undergo further hydrocyanation). 

Hydrocyanation of 1,3-butadiene occurs in three stages. Equation 9.39 shows the first stage, which produces a 2 1 mixture of the desired 3-pentenenitrile (68), produced by a 1,4-addition of HCN to 1,3-butadiene, and the branched isomer 2-methyl-3-butenenitrile (69), which results from Markovinikov 1,2-addition. 

As expected, conjugate addition of HCN predominates leading to 3-pentenenitrile as the major product of the first step, proceeding through a nickel Tr-allyl intermediate. Some... 

Pd[P(OR)3l4, metal salt, boron compound 3-Pentenenitrile Adiponitrile 20 2... 

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