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Diastereomers – We have defined stereoisomers as isomers whose atoms are bonded together in the same order but differ in how the atoms are directed in space. – We have also considered enantiomers (mirror-image isomers) in detail. – All other stereoisomers are classified as diastereomers, which are defined as stereoisomers …

In this subject we will discuss How to draw Fischer projections Introduction to Fischer Projections – We have been using dashed lines and wedges to indicate perspective in drawing the stereochemistry of asymmetric carbon atoms. – When we draw molecules with several asymmetric carbons, perspective drawings become time consuming and …

Racemic Mixtures – Suppose we had a mixture of equal amounts of (+)-butan-2-ol and (-)-butan-2-ol – The (+) isomer would rotate polarized light clockwise with a specific rotation of +13.5o ,and the isomer (-) would rotate the polarized light counterclockwise by exactly the same amount. – We would observe a …

Biological Discrimination of Enantiomers – If the direction of rotation of polarized light were the only difference between enantiomers, one might ask whether the difference would be important. – Biological systems commonly distinguish between enantiomers, and two enantiomers may have totally different biological properties. – In fact, any chiral probe …

– Rotation of the plane of polarized light is called optical activity, and substances that rotate the plane of polarized light are said to be optically active. – There are alot of Organic Compounds have optical activity Introduction to Optical activity Mirror-image molecules have nearly identical physical properties. Compare the …

(R) and (S) Nomenclature of Asymmetric Carbon Atoms – Alanine is one of the amino acids found in common proteins. – Alanine has an asymmetric carbon atom, and it exists in two enantiomeric forms. – These mirror images are different, and this difference is reflected in their biochemistry. – Only …

What is Chirality? – What is the difference between your left hand and your right hand? They look similar, yet a left-handed glove does not fit the right hand. – The same principle applies to your feet. They look almost identical, yet the left shoe fits painfully on the right …

Laws of Osmotic Pressure – From a study of the experimental results obtained by Pfeffer, van’t Hoff showed that for dilute solutions : (a) The osmotic pressure of a solution at a given temperature is directly proportional to its concentration. (b) The osmotic pressure of a solution of a given …

Theories of Osmosis – Here we will discuss some theories of osmosis. – Several theories have been advanced to explain the action of a semipermeable membrane. – It is probable that the mechanism depends on the particular type of membrane used and also on the nature of the solute and …

Determination of osmotic pressure – The osmotic pressure of a given solution can be determined experimentally by the methods detailed below. – The apparatus used for the purpose is often referred to as osmometer. (1) Pfeffer’s Method – The apparatus used by Pfeffer (1877) for determination of osmotic pressure is …

Diffusion and Osmosis – Just as a gas can diffuse into vacant space or another gas, a solute can diffuse from a solution into the pure solvent. – If you pour a saturated aqueous solution of potassium permanganate with the help of a thistle funnel into a beaker containing water, …

The subject of Measurement of freezing point Depression will be discused FREEZING POINT DEPRESSION Relation between Depression of Freezing point and Lowering of Vapour-pressure – The vapour pressure of a pure liquid changes with temperature as shown by the curve ABC, in Fig. – There is a sharp break at …

MEASUREMENT OF BOILING POINT ELEVATION – There are several methods available for the measurement of the elevation of boiling point. – Some of these are outlined below : (1) Landsberger-Walker Method This method was introduced by Landsberger and modified by Walker. Apparatus: – The apparatus used in this method is …

MEASUREMENT OF LOWERING OF VAPOUR PRESSURE (1) Barometric Method – Raoult measured the individual vapour pressure of a liquid and then the solution by this method. – He introduced the liquid or the solution into Toricellian vacuum of a barometer tube and measured the depression of the mercury level. – …

In this subject we will restrict our discussion to Raoult’s Law COLLIGATIVE PROPERTIES – Dilute solutions containing non-volatile solute exhibit the following properties : (1) Lowering of the Vapour Pressure (2) Elevation of the Boiling Point (3) Depression of the Freezing Point (4) Osmotic Pressure – The essential feature of …