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Optical activity occurs due to molecules dissolved in a fluid or due to the fluid itself only if the molecules are one of two (or more) stereoisomers; this is known as an enantiomer. The structure of such a molecule is such that it is not identical to its mirror image (which would be that of a different stereoisomer, or the "opposite enantiomer").
Specific rotation is an intensive property, distinguishing it from the more general phenomenon of optical rotation. As such, the observed rotation ( α ) of a sample of a compound can be used to quantify the enantiomeric excess of that compound, provided that the specific rotation ( [α] ) for the enantiopure compound is known.
Water vapor concentration for this gas mixture is 0.4%. Water vapor is a greenhouse gas in the Earth's atmosphere, responsible for 70% of the known absorption of incoming sunlight, particularly in the infrared region, and about 60% of the atmospheric absorption of thermal radiation by the Earth known as the greenhouse effect. [25]
In all materials the rotation varies with wavelength. The variation is caused by two quite different phenomena. The first accounts in most cases for the majority of the variation in rotation and should not strictly be termed rotatory dispersion. It depends on the fact that optical activity is actually circular birefringence.
Formulae are available for molecules whose shape approximates to that of a symmetric top. [26] The water molecule is an important example of an asymmetric top. It has an intense pure rotation spectrum in the far infrared region, below about 200 cm −1. For this reason far infrared spectrometers have to be freed of atmospheric water vapour ...
Determination of specific rotation: In order to determine a specific rotation of an optically active substance (say, sugar), the polarimeter tube is first filled with pure water and the analyzer is adjusted for equal darkness (both the halves should be equally dark) point. The position of the analyzer is noted with the help of the scale.
Water molecules do not have chirality, therefore they do not have any effect on the measurement of optical rotation. When plane polarized light enters a body of pure water its angle is no different from when it exits. Thus, for water, [] = 0°. Chemicals that, like water, have specific rotations that equal zero degrees are called 'optically ...
The dark brown water in the inland waterways contains high concentrations of CDOM. As this dark, CDOM-rich water moves offshore, it mixes with the low CDOM, blue ocean water from offshore. Colored dissolved organic matter (CDOM) is the optically measurable component of dissolved organic matter in water.