Structure and the Optical Rotatory Dispersion of Saturated Ketones

Moffitt, W.; Woodward, R. B.; Moscowitz, Albert; Klyne, W.; Djerassi, Carl

doi:10.1021/ja01480a015

Cited by 596 publications

(255 citation statements)

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“…38 In the above formalism, dynamic coupling refers to electronic interaction between the chromophore and the perturbers that are neither charged nor polar. The interaction relies on electric quadrupoles induced on the chromophore and electric dipoles induced on the perturbers, and is not static but dynamic in nature, as is manifested in Eq.…”

Section: Electronically Resonant Optically Active Sum Frequency Genermentioning

confidence: 99%

A novel spectroscopic probe for molecular chirality

Shen

2006

Chirality

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Recent advances in developing sum frequency generation (SFG) as a novel spectroscopic probe for molecular chirality are reviewed. The basic principle underlying the technique is brief ly described, in comparison with circular dichroism (CD). The significantly better sensitivity of the technique than CD is pointed out, and the reason is discussed. Bi-naphthol (BN) and amino acids are used as representatives for two different types of chiral molecules; the measured chirality in their electronic transitions can be understood by two different molecular models, respectively, that are extensions of models developed earlier for CD. Optically active or chiral SFG from vibrational transitions are weaker, but with the help of electronic-vibrational double resonance, the vibrational spectrum of a monolayer of BN has been obtained. Generally, optically active SFG is sufficiently sensitive to be employed to probe in-situ chirality of chiral monolayers and thin films. Information on molecular chirality is extremely important because it is directly related to configuration and conformation of molecules, and hence their functional properties. Techniques such as circular dichroism (CD), optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and Raman optical activity (ROA) provide chirality-specific spectroscopic information, from which both the identity and the absolute structure of chiral molecules can be obtained. 1,2 Being optical techniques, they are easily adaptable to various sample geometries and capable of remote in-situ sensing. Therefore, they have been the methods of choice for probing molecular chirality and have contributed enormously to organic chemistry, biochemistry, and pharmaceutical sciences. However, these techniques are known to rely on higher-order responses of the molecular system to the probing light. In other words, the optically active responses would vanish if the interactions involved were only electric-dipole coupling between molecules and light. They become nonvanishing through higher-order interactions, such as magnetic-dipole and electric-quadrupole couplings that are 2 -3 orders of magnitude weaker than electric-dipole coupling. As a result, the sensitivity of these techniques, as determined by the ratio of the chiral response to the achiral response (from pure electric-dipole coupling), is usually not sufficient to detect chirality of monolayers and thin films. On the other hand, the advent of new technologies, such as combinatorial chemistry 3 or the ''lab-on-a-chip,'' 4 requires rapid screening and testing of chemicals of often small quantities, sometimes down to the monolayer level.Moreover, many biological processes involve molecules that either function only when imbedded in a membrane, such as membrane proteins, or accumulate and interact mainly at interfaces. 5 A sensitive probe that allows in-situ study of molecular chirality of such systems would open up new research opportunities and provide new understanding of molecular chirality.In our laboratory, sum freq...

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Section: Electronically Resonant Optically Active Sum Frequency Genermentioning

confidence: 99%

A novel spectroscopic probe for molecular chirality

Shen

2006

Chirality

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“…The relation of χ (2) chiral ∝ XY Z shows that the OA-SFG response follows the same octant rule as CD [48].…”

Section: Dynamic Coupling Model With Amino Acids As a Model System 37mentioning

confidence: 84%

Sum-Frequency Generation from Chiral Media and Interfaces

2006

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Professor Yuen-Ron Shen, Co-chair Professor Richard J. Saykally, Co-chair Sum frequency generation (SFG), a second-order nonlinear optical process, is electric-dipole forbidden in systems with inversion symmetry. As a result, it has been used to study chiral media and interfaces, systems intrinsically lacking inversion symmetry.This thesis describes recent progresses in the applications of and new insights into SFG from chiral media and interfaces.SFG from solutions of chiral amino acids is investigated, and a theoretical model explaining the origin and the strength of the chiral signal in electronic-resonance SFG spectroscopy is discussed. An interference scheme that allows us to distinguish enantiomers by measuring both the magnitude and the phase of the chiral SFG response is described, as well as a chiral SFG microscope producing chirality-sensitive images with sub-micron 2 resolution. Exploiting atomic and molecular parity nonconservation, the SFG process is also used to solve the Ozma problems.Sum frequency vibrational spectroscopy is used to obtain the adsorption behavior of leucine molecules at air-water interfaces. With poly(tetrafluoroethylene) as a model system, we extend the application of this surface-sensitive vibrational spectroscopy to fluorinecontaining polymers.

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“…7 around 285 nm for the cyclohexanone group is negative. Analysis of the Cotton effect according to the olefin octant rule 21) and the cyclohexanone octant rule 22) indicated the rings B/C is trans while the D/E system is cis in 1. Thus, the absolute configuration of 1 was established as shown.…”

Section: Resultsmentioning

confidence: 99%