No abstract

The surface reactions of trans-1,2-dichloroethylene (DCE) on Si(100)-2 × 1 were theoretically investigated to study the effects of chlorine substitutions on surface reactions. As in the case of pristine ethylene, diradical as well as π-complex channels leading to [2 + 2] cycloaddition products were found. In general, chlorine substitution makes the former kinetically more favorable and also changes its stereochemistry. In addition to modifying those existing reaction channels, the chlorine substitution opens new subsequent low-energy pathways leading to the experimentally suggested mono-and dichlorinated adstructures. Their large stabilities with low kinetic barriers make them the major surface species. Current study demonstrates that substitutions not only have large effects on existing reaction channels, but also introduces new possibilities, significantly changing the overall surface reactions.

Three ammonium‐cationic zeolites (ferrierite, ZSM5, and zeolite BETA) are individually analyzed to produce branched‐chain fatty acid (i.e., isostearic acid) from unsaturated linear‐chain fatty acid (ulc‐FA) with up to 98% conversion and 80% selectivity. The SiO2/Al2O3 molar ratio of zeolite, amount of water and choice of additive are found to be the key factors for the efficiency of zeolites in this particular reaction. Detailed characterization of zeolites supports the optimization parameters to produce the best results. Large scale production of isostearic acid achieving a 76% selectivity and 96% conversion demonstrates the potential of this system's capability at the pilot scale. Variation in isomeric composition of branched‐chain fatty acid (bc‐FA) product is observed for the three different catalytic methods. Dimer production due to interaction with the external acidic surface of these zeolites has been observed, but it can be suppressed. Practical Application: Lubricant, cosmetic and surfactant fields are examples where these biodegradable isostearic acid and other bc‐FA materials are applied. Three ammonium cationic zeolites (i.e., ferrierite, BETA, ZSM‐5) are used to produce the iso‐oleic acid (precursor of isostearic acid) with high selectivity. The iso‐oleic acid products are found to have different isomeric compositions which could potentially expand the application of the isostearic acid.

Methacrylanilides, ArN(CH3)COC(CH2LG)=CH2, with allylic leaving groups (LG(-) = BocAla, PhCO2(-), PhCH2CO2(-), PhO(-)) undergo photochemical electrocyclic ring closure to produce a zwitterionic intermediate. Further reaction of the intermediate results in expulsion of the leaving group to give an alpha-methylene lactam as the major product. In addition, a lactam product that retains the leaving group is formed via a 1,5-H shift in the intermediate. Elimination of the leaving group is generally preferred, even for LG(-) = PhO(-), although in benzene as the solvent the lactam retaining the phenolate group becomes the sole photoproduct. The electrocyclic ring closure occurs in the singlet excited-state for the para-COPh-substituted anilide derivative and is not quenched by 0.15 M piperylene or 0.01 M sodium 2-naphthalenesulfonate (2-NPS) as triplet quenchers. Comparable concentrations of 2-NPS strongly quench the transient absorption of the triplet excited state observed at 450-700 nm according to laser flash photolysis experiments. In aqueous media, quantum yields for total products are insensitive to leaving group ability, and Phi(tot)(para-CO2CH3) = 0.04-0.06 at 310 nm and Phi(tot)(para-COPh) = 0.08-0.1 at 365 nm, for which Phi(isc) = 0.15.