![]() Actually to be more technical, it does rotate light but it rotates it in both directions by equal degrees and so the net rotation is zero. One interesting aspect about a racemic mixture is that it is optically inactive, meaning it does not rotate plane polarized light. A racemic mixture is defined as a mixture of equal amounts of the two enantiomer forms of a given chiral molecule. Recall that a chiral molecule is a molecule that contains two nonsuperimposible mirror-images of one another, each called an enantiomer. However, if the light rotates counterclockwise, we call that rotation levorotatory. If the molecule rotates the plane-polarized light in the clockwise direction, we call that rotation a dextrorotatory rotation. A chiral molecule that rotates light is said to be optically active. ![]() The interesting thing about plane polarized light is that chiral molecules have the ability to rotate the plane-polarized light some amount of degrees when the light travels through that molecule. This light is called plane polarized light. This means that the polarizer device screens (or blocks) out all the electric and magnetic fields except the one that moves along one direction. Although light produced by the sun exists in its unpolarized form, we can polarize the light using a special device. Visible light is composed of regions of oscillating electric and magnetic fields that are perpendicular with respect to one another. Optical Activity and Optically Active Molecules In a similar way, molecules are said to be chiral if they have a nonsuperimposable mirror image known as the enantiomer. Our hands are said to be chiral objects because they are mirror-images of one another and are nonsuperimposable. One way in which we can demonstrate this is by using our right and left hand. ![]() Chirality is the ability of a molecule or compound to exist in two nonsuperimposable forms that happen be mirror images of one another. On the other hand, if one of the products completely predominates (or nearly so), then the reaction is said to be regiospecific. Generally speaking, if a reaction takes place that produces two or more products and one of the products predominates, the reaction is said to be regioselective. These terms are regioselectivity and regiospecificity of the reaction. In regiochemistry, which is the study of the orientation of a reaction that deals with an asymmetrical reactant, two terms become very important. T hese lectures vary in length, and will open in a new window when you click on the provided link. The AK Lectures are a series of lectures from a (external) educational platform designed to "promote collaboration between our users and help spread knowledge to every part of the world."
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