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Determination of molecular stereochemistry using optical rotatory dispersion, vibrational circular dichroism and vibrational Raman optical activity
ß 2006 Elsevier B.V. All rights reserved. Chiral Analysis K.W. Busch and M.A. Busch, Eds.
461
CHAPTER 14
Determination of molecular stereochemistry using optical rotatory dispersion, vibrational circular dichroism and vibrational Raman optical activity Prasad L. Polavarapu Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
14.1 OPTICAL ROTATORY DISPERSION 14.1.1 Introduction Optically active or chiral substances rotate the plane of polarization of linearly polarized light passing through a sample of that substance. Such rotation is referred to as optical rotation. At a given concentration, wavelength and temperature, the amount of rotation depends on the molecular structure of that substance. Conversely, it should be possible to determine the molecular structure from the measured optical rotation for an optically active sample. The phenomenon of rotation of plane-polarized light by chemical samples was discovered more than 200 years ago [1,2]. The ‘‘specific rotatory power’’ or ‘‘specific rotation,’’ [], of a liquid is defined as follows: ½ ¼ =l;
ð1Þ
where is the measured optical rotation in degrees, l is the path length of light traversing through the liquid sample, in decimeters (1 decimeter ¼ 100 mm), and is the density of liquid (in g/cc). For solutions, specific rotation is defined as, ½ ¼ 100 =lc;
ð2Þ
where c is grams of chemical substance in 100 cc of solution. An alternate form of Eq. (2) is, ½ ¼ =lc0 ;
References pp. 491–495
ð3Þ
461
CHAPTER 14
Determination of molecular stereochemistry using optical rotatory dispersion, vibrational circular dichroism and vibrational Raman optical activity Prasad L. Polavarapu Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA
14.1 OPTICAL ROTATORY DISPERSION 14.1.1 Introduction Optically active or chiral substances rotate the plane of polarization of linearly polarized light passing through a sample of that substance. Such rotation is referred to as optical rotation. At a given concentration, wavelength and temperature, the amount of rotation depends on the molecular structure of that substance. Conversely, it should be possible to determine the molecular structure from the measured optical rotation for an optically active sample. The phenomenon of rotation of plane-polarized light by chemical samples was discovered more than 200 years ago [1,2]. The ‘‘specific rotatory power’’ or ‘‘specific rotation,’’ [], of a liquid is defined as follows: ½ ¼ =l;
ð1Þ
where is the measured optical rotation in degrees, l is the path length of light traversing through the liquid sample, in decimeters (1 decimeter ¼ 100 mm), and is the density of liquid (in g/cc). For solutions, specific rotation is defined as, ½ ¼ 100 =lc;
ð2Þ
where c is grams of chemical substance in 100 cc of solution. An alternate form of Eq. (2) is, ½ ¼ =lc0 ;
References pp. 491–495
ð3Þ