yaseat in the Senate during the discussion- and to speak to the merits of his right was agreed with on amendment limiting Clag gotts time for speaking to two hours Halos resolution calling on the secretary- of the treasury for copies of the reciprocity agreements under tho last tariff act was taken up and Vest moved the following amendment And that the secretary or- state also inform the Senate whether any steps nave been taken by our authorities to negotate a reciprocal commercial treaty with Mexico and if so what has been done and with what results also that the secre- tary inform the Senate if negotiations wero inaugurated for the purpose aforesaid and have been successful and whathus been the cause of failure I Vest addressed tho Senate in reply to HalEs speech on tho resolution Ho agreed discussion of the question would become the leading issue in the approach- ing national canvass Tho Democratic party had been represented by Hale as be- ing opposed to the policy or reciprocity Vest denied the acsertiou and declared the Democratic party only opposed sham re- ciprocity The arrangement with Brazi did not benefit the American act of Congress could change the inex- orable law of supply and demand which prevented an agricultural people from purchasing agricultural products The market for American agricultural pro- ducts was in Great Britain not in South America Why stop with South America- and sugar Why exclude shoddy and cloth ingi Genuine reciprocity was free trade Hale said what the Democratic party wanted and believed in was Simon pure free trade Halo read a newspaper par graph showing the increased imports nt Cuba of American flour since the re- ciprocity arrangement went into effect and said the four of Spain had been driven of that market Reciprocity said Halo had been made tho Republican policy it would go before the American people in the next campaign and there was not a miner laborer farmer or shipper who was not interested in Its suc cessVest replied that the fundamental doctrine of the Democratic party was freer trade and larger intercourse with the whole word The incroatfo of the import of flour into Cubivv proved that the Democratic party was right and that when duties were put down exports in- creased The Republicans in inserting the reciprocity section in the McKinley hill tad attempted to get out of Its difficulty by stealing a portion of Democratic doctrine the tariff discussion closed without action- on the resolution or amendment but with- an intimation several other Senators would take part in the discussion The Idaho election case was taken up1 and after argument by Vance in favor of Claggett the Senate adjourned

We show how the bond-bond polarizability index, as originally introduced by Coulson and Longuet-Higgins in the Hückel-theoretic context, can be generalized in the natural bond orbital (NBO) framework to ab initio molecular orbital and density functional theory levels. We demonstrate that such a "natural bond-bond polarizability" (NBBP) index provides a flexible and quantitative descriptor for a broad spectrum of delocalization effects ranging from strong π aromaticity to weak intra- and intermolecular hyperconjugative phenomena. Illustrative applications are presented for representative delocalization effects in saturated and unsaturated species, chemical reactions, and hydrogen-bonding interactions.

The Birch Reduction is one of the main reactions of organic chemistry. The reaction involves the reaction of dissolving metals in ammonia with aromatic compounds to produce 1,4-cyclohexadienes. Discovered by Arthur Birch in 1944, the reaction occupies 300 pages in Organic Reactions to describe its synthetic versatility. Thus, it is remarkable that the reaction mechanism has been so very controversial and only relatively recently has been firmly established. Perhaps this is not that surprising, since the reaction also has many unusual and esoteric mechanistic facets. Here, I provide a description of how I have applied ever-evolving levels of quantum mechanics and a novel experimental test to understand details of the mechanism and the origins of the selectivities observed in the Birch reduction. The reaction involves an initial radical anion resulting from introduction of an electron from the blue liquid ammonia solution of free electrons formed by the dissolution of Li or related metals. This radical anion is protonated by an alcohol and then further reduced to a carbanion. Finally, the carbanion is protonated using a second proton to afford a nonconjugated cyclohexadiene. The regiochemistry depends on substituents present. With 18 resonance structures in the case of anisole radical anion, prediction of the initial protonation site would seem difficult. Nevertheless, computational methods from Hückel theory through modern density functional calculations do correctly predict the site of protonation. An esoteric test established this mechanism experimentally. The nature of the carbanion also is of mechanistic interest, and the preponderance of the resonance structure shown was revealed from Hückel calculations involving variable bond orders. For the trianion from benzoic acid, parallel questions about structure are apparent, and have been answered. Some mechanistic questions are answered experimentally and some by modern computations. Recently, our mechanistic understanding has led to a variety of synthetic applications. For example, the preparation of alkyl aromatics from benzoic acids makes use of the intermediates formed in these reactions. This Account provides an overview of both experimental techniques and theoretical methodology used to provide detailed mechanistic understanding of the Birch Reduction.

The title compound, C19H16O2, was isolated as the major product after the solid-state photochemical reaction of 2-methoxy-4,4-diphenylcyclohexa-2,5-dienone. The dihedral angles between the central ring and pendant benzene rings are 60.76 (6) and 51.64 (6)°. The O—C vector of the methoxy group is almost perpendicular to the plane of the central ring as indicated by the C—C—O—C torsion angle of 94.89 (18)°. Hydrogen-bonded dimers are formed in the crystal structure via O—H⋯O interactions. The data were collected at room temperature on a Bruker SMART X2S diffractometer in the automated mode and processed manually thereafter.

Our research on the triplet photochemistry of vinylcyclopropenes has dealt with a diverse series of systems, providing a series of experimental examples and mechanstic studies. It perhaps is not surprising that the reaction mechanisms have been controversial. The present study is theoretical and provides evidence for control by a critical T(1) diradical intermediate which has a high spin-orbit coupling with S(0) ground-state along the mechanistic pathway. The evidence now for the one pathway derives from independent generation and behavior of this diradical, prediction of the reaction regioselectivity in nine diverse examples, the S(0) and T(1) hypersurfaces in the reaction, and an S(0)-T(1) degeneracy with SOC for the critical diradical. This triplet diradical when independently generated gives the same regioselectivity observed in examples starting with the vinylcyclopropene triplet itself. The overall reaction provides a useful synthesis of cyclopentadienes.

The Type-A photochemistry of cyclohexadienones is well-studied and follows a well-established mechanistic pathway. One early example is the rearrangement of santonin to lumisantonin. Another example is the rearrangement of 4,4-diphenylcyclohexa-1,5-dienone. Remarkably, replacement of one carbon by nitrogen alters the reaction course to give a regioselective phenyl migration.

2,3-Diphenyl-1-naphthol (1) undergoes two unexpected reactions under different conditions. Compound (1) was heated in DMSO-d6 and underwent a Pummerer type thermal reaction to give two isomeric products, 1-(methylthio)methoxy-2,3-diphenyl naphthol-d5 which crystallized in the space group \( P{\bar{\text{1}}} \) with a = 7.1610(9) Å, b = 11.2795(15) Å, c = 12.8905(17) Å, α = 114.049(2)°, β = 96.589(2)°, and γ = 102.945(2)°, and 2-(methylthio)methyl-2,3-diphenyl 1(2H)-naphthalenone-d5 which crystallized in the space group \( P{\bar{\text{1}}} \) with a = 8.5981(5) Å, b = 10.4374(6) Å, c = 11.1078(6) Å, α = 78.748(2)°, β = 67.709(2)°, and γ = 83.184(2)°. Photolysis (254 nm) of (1) resulted in 2,2′,3,3′-tetraphenyl-1,1′-bi-2-naphthol which crystallized in the space group P21/c with a = 26.3616(11) Å, b = 10.1707(4) Å, c = 23.3376(9) Å, and β = 99.034(2)°.

There has been some controversy about the mechanisms of reactions of enones and dienones. The question has been whether a zwitterion or diradical is involved as the intermediate. In the case of ground state species it has not been recognized that zwitterions may have diradical character. In triplet reactions there is the question of whether the rearrangements take place at the initial T1 stage or subsequently as SO ground state zwitterions or diradicals. We now have some new rearrangements bearing on these questions. In some cases it is the triplet which rearranges, while in others it is the SO zwitterion. The zwitterion vs. diradical nature of the SO species has been assessed by both experimental as well as theoretical means. Similarly, both experiment and computational theory have been used to determine at what stage the triplet rearrangements occur and to determine the characteristics of the rearranging species. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).

This exposition summarizes a personal perspective on past and current developments in organic photochemistry. It comprises three portions. The first section describes the beginnings of our photochemical studies and how it was possible to relate photochemical reactivity to excited-state electronic structures. The second selectively relates some of the reactions and concepts developed in the intermediate years. Finally, the third portion describes our recent research.

In contrast to the photochemistry of monocyclic aza-cyclohexenones, their counterparts with a second carbonyl group undergo photochemical rearrangements which parallel those of the 4,4-disubstituted cyclohexenones.

A decalyl framework with a siloxy enolic moiety and proximate proton transferring groups was synthesized. On enolate generation with fluoride two competitive reaction modes were possible: (a) intermolecular protonation, and (b) intramolecular proton transfer by the proximate group. Control of the protonation stereochemistry proved possible by varying the proximate group and by changing the acidity of the medium. With the groups -CH2OH, -CH=O, and -CH2OCH2OCH3 as the proximate groups, only intermolecular proton transfer was observed with no dependence on acidity. In contrast, with -COO- and COOH, only intramolecular protonation resulted but again with no dependence on acidity of the medium. In contrast, with -CH2NH2 as the proximate group, intramolecular proton transfer predominated with a dependence on the effective pH of the medium. A kinetic analysis provided a linear-log relationship of the ratio of the two stereoisomers with the medium acidity. The analysis revealed that two acetic acid molecules are involved in providing the proton to the enolate moiety. A theoretical analysis was developed paralleling the experimental results. In the ketonization transition state, the hybridization was shown to be close to sp2 hybridized at the alpha-enolate carbon.

A priori, allenic enolates as reaction intermediates may be protonated to afford (Z)- or (E)-alpha,beta-unsaturated carbonyl products. The allenic enolates are tautomeric with alpha-vinylcarbanions. The literature on the behavior of these species on protonation is highly varied both in stereochemical outcome and in mechanistic interpretation. The current study has provided an independent mode of generation of the allenic enolates and has investigated the reaction stereochemistry of protonation to afford the stereoisomeric alpha,beta-unsaturated carbonyl products. Under kinetic conditions, these highly reactive species are protonated in the alpha,beta-pi plane with preference (E) to the larger beta group. Under thermodynamic conditions, addition/elimination equilibrates the two product stereoisomers. The kinetic protonation stereochemistry is a function of solvent, proton donor, and donor concentration. Computations serve to clarify the reaction mechanism. It was found that the stereochemistry of ketonization of allenic enolates follows the reaction course suggested as possible some decades earlier and common to less unique enolates. Additionally, the linear versus the bent enolate structure proves to depend on the countercation. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).

The photochemistry of the heterocycle 5,6-dihydro-1-methyl-5,5-diphenylpyridin-2(1H)-one (compound 1 in the text) leads to two competitive reactions (the reactions are depicted in the Introduction to the article). These arise from fission of bond a, between the nitrogen (N-6) and C-1, and bond b, between C-4, with the two phenyl substituents, and C-5, adjacent to the nitrogen. Scission of bond a alone leads to a zwitterionic intermediate which can be trapped by nucleophiles, while cleavage of bonds a and b together affords two fragments--a ketene and an imine. The ketene could be intercepted with nucleophiles and the imine trimerized. Computation reveals little weakening of bonds a and b. But as stretching begins, conical intersections are encountered, leading to ground-state products.

[reaction: see text] Proton transfer in ketonization of enolates is a critical step in a myriad of organic reactions. Its stereochemistry has been the object of our studies since we reported kinetic protonation from the less hindered face of the molecule under kinetic control some decades ago. Very recently, we have succeeded in reversing the stereochemistry using 2-pyridyl groups to deliver the proton. We now report intramolecular delivery by other moieties and control of intramolecular versus intermolecular proton delivery.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

AbstractFor Abstract see ChemInform Abstract in Full Text.

[reaction: see text] A unique new set of reactions has been observed in heterocyclic photochemistry. 2-Methyl-4,4-diphenyl-3,4-dihydropyrimidin-1(2H)-one has been synthesized and its photochemistry investigated. This compound has been found to lead to a rearranged, dimeric product arising from a unique bond-scission process.

The photochemistry of 13 4,4-diphenylcyclohexenones, substituted at carbon-6, was investigated in solution and in the crystalline state. The stereoselectivity was of particular interest. In the solution photochemistry of C-6 monosubstituted enones in benzene, there was a unique preference for migration of the cis-phenyl group with formation of bicyclo[3.1.0]hexanone photoproducts, with the original 6-substituent having an endo configuration at carbon-3 of the product. In methanol the reaction was diverted to afford 3,4-diphenylcyclohex-2-enes understood as arising from a hydrogen-bonded zwitterionic intermediate. The solid-state photochemistry was also investigated. There was a dramatic absence of the 3,4-diphenylcyclohex-2-ene products in accord with the absence of the hydrogen bonding encountered in methanol. Further, the solid-state reactivity correlated with a vector analysis using X-ray atomic coordinates. This established that the migrating phenyl group required an orientation facing the enone beta-carbon. While the interesting preference for the cis-endo migration was not intuitively predicted, ab initio computations on the alternative phenyl-bridged triplet intermediates did lead to an understanding of the selectivity.