Peter V. Alston

A transition state FMO approach for prediction of the regioselectivity of the Diels-Alder reaction

Abstract The regioselectivity in the Diets-Alder reaction of 1-substituted-1, 3-butadienes can be completely explained by FMO theory when the frontier molecular orbitals of the reactants in the concerted transition state are considered. This excellent agreement between theory and experimental results from the more realistic representation of the ionic polarization at the primary carbon sites.

Effect of Yarn Spinning System on Pill Resistance of Polyester/Cotton Knit Fabrics

We have determined the effect of ring, rotor, and air-jet spinning on the pill resistance of jersey and interlock fabrics. The jersey fabrics contained the same polyester type, while the interlock fabrics contained the preferred polyester for each spinning system. In each of the constructions, the air-jet spun fabrics were significantly more pill resistant than ring and rotor spun fabrics. Kinetic studies of the rates of pill formation and wear-off indicate that this difference is due to the much slower formation rate of the air-jet spun fabric. Analysis of pill character suggests that the tightly wrapped structure of the air-jet yarn inhibits the formation of free ends of polyester, which are the primary cause of the pills. Pill resistance for the ring spun fabric was only slightly better than for the rotor spun fabric when the same polyester type was used.

Effect of fiber cross section on rotor spinning of polyester

The effect of polyester fibers with nonround cross sections on the rotor spinning of 100% polyester and 50% polyester/50% cotton yarns is determined. The polyester cross sections are hollow with a 5% void and trilobal, oval, ribbon, peanut, and scalloped oval shapes. The polyester fibers (oval, ribbon, peanut, scalloped oval shapes) with aspect ratios greater than one have fewer yarn breaks than the stiffer polyester fibers (round, hollow, trilobal shapes) with an aspect ratio of one. The peanut and scalloped oval fibers, which combine a multilobal character with an aspect ratio greater than one, have the fewest yarn breaks. The superior rotor spinning of these nonround fibers is believed to be the result of enhanced twist propagation due to lower torsional rigidity and lower fiber-to-surface contact.

Azatricycles from substituted pyridines. Synthesis and rearrangement of N-ethoxycarbonyl-2-azatricyclo[4.3.1.03,7]dec-8-enes.

Abstract The scope and relative rates of intramolecular cycloaddition reactions of methyl-substituted 2-[3-butenyl]-1,2-dihydropyridines 4 have been studied. Cycloadducts 5 can be rearranged to 14 upon reaction with bromine, except when olefinic methyl groups are present.

Regioselective Synthesis of 4-, 5-, and 6-Alkyl and Dialkyl 5,6-Dehydroisoquinuclidines from Phenylvinylsulfone Cycloadducts of N-Ethoxycarbonyl-1,2-Dihydropyridines

Abstract A regioselective route to 4-, 5-, and 6-alkyl or 4,5-, 4,6-, and 5,6-dialkyl-5,6-dehydroisoquinuclidines 1a-f is described.

Effect of Denier-per-Filament of Polyester on Yarn Strength in Open-End Rotor Spinning

There is considerable interest in replacing fine ring spun yarns with fine rotor spun yarns for uniforms and career apparel because the cost of yarn manufacture is much lower with rotor spinning than with conventional ring spinning. However, rotor spun yarns are inherently weaker than ring spun yarns. The effect of the denier-per-filament (DPF) of polyester on the yarn strength of rotor spun yarns is investigated and com pared to the ring spun counterparts. The strengths of both rotor and ring spun yams increased linearly with a decrease in the DPF of the polyester, and the magnitude of the change was the same for both spinning systems. The strengths and elongations of the ring spun yarns were 44% and 37% higher than those of the rotor spun yarns when the same polyester was used. The strength of the rotor spun yarn increased 23% over the DPF range that is commercially available.

Unexpected rate retardation by 4-alkyl substituents in neutral electron demand diels-alder reactions of 2-(3-butenyl)-1,2-dihydropyridines

Abstract Sustmanns equation gives insight into the slower intramolecular reactivity of 4-alkyl-2-(3-butenyl)-1, 2-dihydropyrldines 2a – 2f relative to the parent 1a . Steric effects are inconsistent with the observed rate data.

Deposit Generation in the Open-End Spinning of 100% Polyester Yarn

that the needles caused different degrees of consolidation, with the result that the finer needles showed higher fabric thickness and the coarser needles reduced thickness. The thickness of the fabrics was partly related to consolidation and partly to stretch during needling. The needle parameter most related to fabric thickness was the depth of undercut d, a parameter not previously thought to be important. We think the importance of d is due to its being related to both 0 and LI, since as either 0 or L, increases so does d In our analysis of variance, we considered the filtration response using two sources of variations-needle types and sizes-and four pressure levels plus the interaction. The computed critical F value for the 5% level of significance obtained was 2.59 > 2.16. Since