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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.
For example, if a solution of β-D-glucopyranose is dissolved in water, its specific optical rotation will be +18.7°. Over time, some of the β-D-glucopyranose will undergo mutarotation to become α-D-glucopyranose, which has an optical rotation of +112.2°. The rotation of the solution will increase from +18.7° to an equilibrium value of +52 ...
Of note, the L form of amino acids and the D form of sugars (primarily glucose) are usually the biologically reactive form. This is due to the fact that many biological molecules are chiral and thus the reactions between specific enantiomers produce pure stereoisomers. [5] Also notable is the fact that all amino acid residues exist in the L form.
Glucose is a sugar with the molecular formula C 6 H 12 O 6.It is overall the most abundant monosaccharide, [4] a subcategory of carbohydrates.It is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight.
If there are -many optically active different chemicals ('chemical species') in a solution and the molar concentration (the number of moles of each chemical per liter of liquid solution) of each chemical in the solution is known and written as (where is a number used to identify the chemical species); and if each species has a specific rotation ...
Le Bel-van't Hoff rule states that for a structure with n asymmetric carbon atoms, there is a maximum of 2 n different stereoisomers possible. As an example, D-glucose is an aldohexose and has the formula C 6 H 12 O 6. Four of its six carbon atoms are stereogenic, which means D-glucose is one of 2 4 =16 possible stereoisomers. [20] [21]
The three moments of inertia have different values. Examples of small molecules that are asymmetric tops include water, H 2 O and nitrogen dioxide, NO 2 whose symmetry axis of highest order is a 2-fold rotation axis. Most large molecules are asymmetric tops.