Activity 9: Polarimetry Flashcards
Ordinary light when passed thru a polarizer becomes a ______
polarized light
The so-called rotation of the plane of the polarized light is caleed __________
opticall-active
Instrument used to detect/measure the optical activity of a chiral compound
Polarimeter
has to be rotated the same number of degree in the same directions as the rotated light
Analyzer
It is attached to the analyzer to permit us read the optical rotation, the angle between the original and final planes of poarization
dial
The direction of the rotation maybe ___________
clockwise (+) or counterclockwise (-)
The magnitude of rotation depends upon the _________
number of optically active molecules the light encounters in passing thru the sample
Factors affecting the amount of rotation:
- length of the middle tube
- density of the liquid
- conc. of the solution
- nature of the sample and solvent
- wavelength of the plane-polarized light used
- temperature
In the experiment, what kind of polarimeter was used
Rudolph Polarimeter
Rudolph Polarimeter
light source: _______
Range: ________
Length of sample cell: ________
Tungsten lamp at 5893 A
-90 deg. to +90 deg.
2 dm
The point when the halves of the circle are of equal intensity and of low brightness.
matchpoint
Why will an air bubble in the light path of the sample change the observed rotation?
because air bubbles in light path of the solution reduces the amount of chiral molecules that will be encountered by the radiation
3 reasons why sucrose exhibits optical activity:
- It has no plane of symmetry
- it’s a CHIRAL structure
- It contains several chiral centers
Explain why water is an appropriate solvent in the experiment
Water is optically inactive or achiral due to the bent structure of the water molecule, which possesses a plane of symmetry. Thus, it will bring no effect on it.
In the case of sucrose, explain briefly the effect of temperature on its specific rotation
Generally, as the temperature increases, the specific rotation of sucrose tends to decrease. This behavior is attributed to the fact that molecular interactions and conformational changes in sucrose molecules are influenced by temperature. The specific rotation of sucrose is often measured at a standardized temperature, such as 20 degrees Celsius, to ensure consistent and comparable results in polarimetric experiments.
