Tert-butyl Perbenzoate Research Articles

N-Methylation of carbamate derivatives of α-amino acids

Carbamate derivatives of α-amino acids react by N-methylation, without racemization, on treatment with tert-butyl perbenzoate in the presence of copper(II) octanoate; the selective reaction of N-tert-butoxycarbonylglycine methyl ester, in preference to the corresponding alanine and valine derivatives, indicates that the relative reactivity of substrates is determined by the comparative ease of their complexation to the copper.

Effect of free-radical release on diesel ignition delay under simulated cold-starting conditions

Peak compression temperatures typical of those achieved when cranking a cold diesel engine can be produced by running a gasoline engine of compression ratio 7.5, with a block temperature of 100°C. Under the chosen operating conditions, diesel fuel of cetane index 43 would ignite only very feebly, with ignition delays in excess of about 9 ms, but in the presence of various additives, iso-octyl nitrate, di-tert-butyl peroxide, tert-butyl perbenzoate, 1,1-di-(tert-butylperoxy) cyclohexane, and 1,1-di-(tert-butylperoxy) 3,3,5-trimethyl cyclohexane, ignition delays of between 3 and 7 ms were observed; although the thermal decomposition rates of these additives span approximately a factor of 60, the ignition delays do not correlate with these rates. Some measurements were made on the effect of diethyl ether, either blended with the fuel or bled into the air intake: its efficacy as a cold-starting aid stems from the fact that diethyl etherair mixtures ignite spontaneously during the compression stroke, thereby causing the fuel to ignite as well.

Crosslinking of polypropylene–polyethylene blends by peroxide and the effect of pentaerythritol tetrallyl ether

AbstractCrosslinking of polypropylene–polyethylene (PP‐PE) blends involving 10, 20, 30, 40, 50, 60, 70, 80, and 90% of PP with dicumylperoxide (DCP) or tert‐butyl perbenzoate (TBPB) and in the presence of coagent pentaerythritol tetrallyl ether (PETA) was investigated at 180°C. It was found that at lower concentrations of peroxide alone (e.g., 2.5% of DCP) only PE component is crosslinked in all compositions of PP‐PE blends. In the crosslinking of PP‐PE 50:50 with 4% of TBPB, insoluble gel was obtained, which contained 13% PP and 87% PE. If 2% PETA was also used, the portion of PP in gel increased to 39%; the total yield of gel in PP‐PE blend increased from 50 to 70%. The lower crosslinking efficiency of coagent PETA in the PP‐PE blends compared with PP alone is associated with better solubility of the coagent in the PE phase in contrast to the PP phase. The coagent does not particularly raise the crosslinking efficiency of peroxide in PE, but increases it in the PP phase. A remarkable decrease in melting temperature and temperature of crystallization of both polymer components depending on peroxide concentration was found by calorimetric measurements.

Selective crosslinking of the elastomer phase in high-impact polysterene

The mechanism of crosslinking in the elastomer phase of high impact (HIPS) polystyrene is considered and the requirements for the crosslinking initiator are formulated. For elastomers of low reactivity, particularly, the importance of selective dispersion of the initiator in the elastomer phase is indicated. It was shown experimentally that tert-butyl perbenzoate, normally used for crosslinking the diene rubber phase in HIPS, was ineffective for crosslinking HIPS containing a slightly unsaturated silicone as the elastomer phase. Oligodimethylsiloxane with terminal peroxy groups, which is not very compatible with styrene-polystyrene blends but readily compatible with the rubber, was shown to be an effective crosslinking agent. Crosslinking of the elastomer phase was shown to result in a substantial increase in the impact resistance of the material.

ChemInform Abstract: STERIC CROWDING AND THE REACTIVITY OF SUBSTITUTED TERT.‐BUTYL PERBENZOATES

The relative rates of decomposition of peroxyesters in cumene at 100° and their activation parameters ΔH≠ (kcal/mol) and ΔS≠ (cal deg−1 mol−1) were tert-butyl perbenzoate (1) 1.0, 34.0, 9.3; tert-butyl pertoluate (7) 1.3, 32.2, 4.8; tert-butyl permesitoate (8) 11, 31.9, 8.4; and tert-butyl 2,4,6-tri-tert-butylperbenzoate (9) 29, 32.9, 13.0. Each peroxyester yielded the corresponding acid as one of the products. The reactions are all interpreted as proceeding through a rate-determining scission of the O—O bond to yield a benzoyloxy radical, which then undergoes competitive decarboxylation and hydrogen abstraction from the solvent. The small rate acceleration due to a para substituent is interpreted as due to a polar factor and the larger rate enhancing effect of the ortho substituents is interpreted as due to destabilization of the ground state due to twisting of the carboxyl group out of conjugation with the ring.

Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

The relative rates of decomposition of peroxyesters in cumene at 100° and their activation parameters ΔH≠ (kcal/mol) and ΔS≠ (cal deg−1 mol−1) were tert-butyl perbenzoate (1) 1.0, 34.0, 9.3; tert-butyl pertoluate (7) 1.3, 32.2, 4.8; tert-butyl permesitoate (8) 11, 31.9, 8.4; and tert-butyl 2,4,6-tri-tert-butylperbenzoate (9) 29, 32.9, 13.0. Each peroxyester yielded the corresponding acid as one of the products. The reactions are all interpreted as proceeding through a rate-determining scission of the O—O bond to yield a benzoyloxy radical, which then undergoes competitive decarboxylation and hydrogen abstraction from the solvent. The small rate acceleration due to a para substituent is interpreted as due to a polar factor and the larger rate enhancing effect of the ortho substituents is interpreted as due to destabilization of the ground state due to twisting of the carboxyl group out of conjugation with the ring.

Study of the influence of dodecyl mercaptan, tert-butyl perbenzoate, and surface-active substances on the joint spectrophotometric determination of styrene and acrylonitrile in aqueous solutions

Study of the influence of dodecyl mercaptan, tert-butyl perbenzoate, and surface-active substances on the joint spectrophotometric determination of styrene and acrylonitrile in aqueous solutions

Radical polymerization of N‐vinylcaprolactam in homogeneous solution. II

AbstractThe polymerization of N‐vinylcaprolactam in toluene, dioxane, chlorobenzene, dimethylformamide, and ethylene carbonate with various peroxides, perbenzoates and azobisisobutyronitrile as initiators at 60–80°C, was studied. Under these conditions azobisisobutyronitrile and tert‐butyl perbenzoate have satisfactory activity as initiators. Under these conditions N‐vinylcaprolactam polymerization in homogeneous solution is first order towards the monomer and 0.5 order towards the initiators.