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Molecular mechanics calculations on cycloheptadiene indicate that the molecule has a structure which undergoes a wide pseudorotational motion between two C1 forms, and a C1 form, and this structure is in equilibrium with the C2 form. It is shown that this equilibrium mixture is consistent with all of the available experimental data. 相似文献
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Alan P. Sprague 《Geometriae Dedicata》1984,16(2):149-156
A special Laguerre plane is a nondegenerate transversal 3-design such that the residue of each point is a dual affine plane. A special Laguerre plane is equivalent to an optimal code with three information digits and maximal length. An extended dual affine plane is an incidence structure (whose objects will be called points and blocks) such that the residue of each point is a dual affine plane, and each pair of points is in at least one block. Finite extended dual affine planes exist only of order 2, 4, and (dubiously) 10. We show that any finite incidence structure having the residue of each point a dual affine plane either is a transversal 3-design or has a block through each pair of points. Hence theorem: If a finite nondegenerate connected incidence structure has the residue of each point a dual affine plane, then is either an extended dual affine plane or a special Laguerre plane.
This research was partially supported by NSF Grant MCS-8102361. 相似文献
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Abstract— By means of in situ photolysis EPR of aqueous solutions of α-oxocarboxylic acids (RCO-CO2 H) at pH values above 5, semidione radical anions [RC(O- )=C(O')R] and α-hydroxy-α-carboxy alkyl radicals [RC(OH)CO2 -] were detected. C02 was identified as a reaction product. On photolysis of mixtures of α-oxocarboxylic acids (RCOCO2 H and R'COCC2 H), "mixed" semidione radical anions [RC(O- >=C(O)R'] were observed in addition to RC(O- )=C(O')R, R'C(O- )=C(O')R', RC(OH)CO2 - and R'C(OH)CO2 - . The experimental results are explained in terms of photodecarboxylation (α-clea-vage) of electronically excited RCOCOJ to yield RCO and CO2 . The radicals RC(OH)CO2 - are formed by reduction of RCOCO2 - by CO2 - . The semidione radicals are produced by addition of RCO to RCOCO2 - followed by decarboxylation of the intermediate adduct. This mechanism was confirmed by generating acyl radicals independently and reacting them with α-oxocarboxylic acids. Selected product studies support the mechanism suggested. 相似文献
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Liu JF Ye P Sprague K Sargent K Yohannes D Baldino CM Wilson CJ Ng SC 《Organic letters》2005,7(15):3363-3366
[reaction: see text]. Total syntheses of deoxyvasicinone (1), mackinazolinone (2), and 8-hydroxydeoxyvasicinone (3) via novel microwave-assisted domino reactions, as well as a novel three-component one-pot total synthesis of isaindigotone (5) promoted by microwave irradiation, are reported. The efficient reaction process enabled us to rapidly access related natural product derivatives and to identify a new class of cytotoxic agents. 相似文献