Stereochemistry: Optical Activity of Chiral Molecules Essay Example

and to a certain degree on the temperature as well.

However, the temperature effect is very difficult to pacify since it differs for each compound. Generally the following equation is used to calculate the specific optical rotation from experimental data: Normal monochromatic light contains light that possesses oscillations of the electrical field in all possible planes perpendicular to the direction of propagation. When light is passed through a polarize only light oscillating in one plane will leave the polarize. This linear polarize light can be described as a superposition of two counter-rotating components, which propagate with different velocities in an optical active medium.

If one component interacts stronger than the other with a choral molecule, it will slow down and therefore arrive later at the observer. The result is that the plane of the light appears to be rotated.

Key words: Optical Rotation: the rotation of the plane of popularization of plane-polarize light by an optically active substance. Chemical analysis) for determining the effect of a substance in rotating the plane of popularization of light. Methanol: a toxic, colorless, volatile flammable liquid alcohol, originally made by distillation from wood and now chiefly by oxidation methane. Results:

Rotation is given in +1- degrees, depending on whether he sample has R- (positive) or S- (negative) moisteners.

The standard measurement for rotation for a specific chemical compound is called the specific rotation, defined as an angle measured at a path length of 1 decimated and a concentration of leg/ml. "The olfactory system sensitively discerns scents from many small molecules as the brain analyses signals from nasal receptors. " These receptors are selective to some degree, though the mechanism for selectivity

is still debatable.

Moisteners, choral assessing proposed mechanisms. There is a correlation between molecular structural) flexibility and whether or not the left- and right-handed moisteners smell the same. In particular, for the fairly extensive class of moisteners with six- member ring flexibility, moisteners do not smell the same.

There are, of course, significant experimental uncertainties. This is the structure of limestone, and as you can see it is a 6-ring molecule. This molecule is very flexible due to the carbon bonds. That flexibility is what gave the lemon citrus smell. We describe the flexible molecules containing six-member rings for which any one of the following three possible structures.

The first group of flexible molecules includes those having CICS-trans transitions about the six-member ring. These correspond to molecules where two functional groups lie across the plane of the ring, and where it is feasible that these groups can isomerism by switching between sides of the plane. Second, there are molecules whose flexibility stems from cyclopean ring twist transitions from chair to boat conformations. Third, there are those molecules for which cyclones ring twists are possible, similar to cyclopean chair-boat, but more strained.

The molecule is flexible because the bond angles are lose to the geometrical angle of a hexagon as well as the limited amount of torsion's strain due to staggered conformations of the hydrogen's bonded to each carbon in the ring. Therefore we can conclude that the moisteners smell different because the molecules are flexible and interact with different olfactory receptors.

This is why our unknowns all smell different because each one has it's own characteristic of either they way its flexible, the way the molecule is formed

or it could be anything, because no moisteners smell exactly the same. Measurement of optical rotation is performed using an instrument called a alerter. Here is how it works. Plane-polarize light is first obtained by passing light through a polarize.

If this polarize light is passed through a second filter (analyzer) oriented parallel to the first, the maximum amount of light reaches our eye. If the orientation of the analyzer is rotated, the amount of light being transmitted declines (I. E. The light dims). The polarities initially has the analyzer oriented perpendicularly to the polarize so that the transmission of light is at a minimum.

When an optically active (choral) material is placed between the polarize and analyzer, the popularization vector of the light is rotated as described above, and the amount of light able to pass through the analyzer increases, I. E. T will appear the angle through which the analyzer must be rotated is a measure of how much rotation was produced by the sample solution. From this optical rotation, we calculated the specific rotation using Boots Law. With the specific rotation, and the table 1 in the lab manual (peg L-1 1), we were able to figure out our unknown giving for part.

Conclusion:

Optical activity is the ability of a choral molecule to rotate the plane of plane- lordlier light. It is measured using a polarities, which consists of a light source, popularizing lens, sample tube and analyzing lens. When light passes through a sample that can rotate plane-polarize light, the light appears to dim to the eye because it no longer passes straight through the popularizing filters. The amount of rotation is

quantified as the number of degrees that the analyzing lens must be rotated by so that it appears as if no dimming, of the light has occurred. When rotation is quantified using a polarities it is known as an observed rotation, because rotation s affected by path length (l, the distance the light travels through a sample) and concentration (c, how much of the sample is present that will rotate the light).