On introducing a polarimeter tube 40 decimeter long and containing sugar solution of unknown strength, it is found that the plane of polarization is rotated through angle 25º. Find the strength of sugar solution in gm /cm3. Specific rotation of sugar solution 50º per centimeter per unit concentration.
Answers
Answer:
Most physical properties of enantiomers i.e., melting point, boiling point, refractive index, etc. are identical. However, they differ in a property called optical activity, in which a sample rotates the plane of polarization of a polarized light beam passing through. This effect was first discovered in 1808 by E.L. Malus (1775-1812), who passed light through reflective glass surfaces. Four years later, J.B. Biot (1774-1862) found that the extent of rotation of the light depends on the thickness of the quartz plates that he used. He also discovered that other compounds i.e., turpentine and sucrose solutions were capable of rotating the light. He attributed this "optical activity" to certain features in their molecular structure (asymmetry). Based on his research, he designed one of the first polariscopes, and formulated the basic quantitative laws of polarimetry. In 1850, Wilhelmy used polarimetry to study the reaction rate of the hydrolysis of sucrose. In 1874, van't Hoff proposed that a tetrahedral environment of the carbon atom could explain the phenomenon of optical activity. Today, polarimetry is used routinely in quality and process control in the pharmaceutical industry, the flavor, fragrance and essential oil industry, the food industry, and the chemical industry. The optical purity of the product can be determined by measuring the specific rotation of compounds like amino acids, antibiotics, steroids, vitamins, lemon oil, various sugars, and polymers and comparing them with the reference value (if the specific rotation of the pure enantiomer is known).