In stereospecific reactions, one stereoisomer of the product is obtained if one stereoisomer of the reactant is present, while different stereoisomers of product are obtained when different stereoisomer of the reactant are present. Thus for determining whether a reaction is stereospecific or not, one has to analyse the product ratio from the different stereoisomer of
Stereospecific and Stereoselective Reactions Read More »
Conformational isomerism: Isomers resulting from different arrangements of the atoms in space due to the rotation of groups around C-C bond axis are known as conformational isomers. The study of these confirmations or conformational isomers is known as conformational analysis which involves analysis of the shapes that molecules can adopt by rotation about single bond.
Conformational Isomerism – Pedagogy Zone Read More »
Following nomenclature system are used for naming of geometrical isomers: cis and trans nomenclature, E and Z nomenclature, and Syn and Anti nomenclature. cis and trans Nomenclature In a molecule having a carbon-carbon double bond, with four groups or atoms directly attached to the two carbon atoms, where all atoms are present in the same plane thus
Nomenclature of Geometrical Isomers Read More »
The optically active compounds exist in two or more isomeric form and they differ in their optical activity. The isomers which have same chemical reactions and almost same physical properties but differ in their behaviour towards polarized light are optical isomers and the phenomenon is known as optical isomerism. The two main types of optical
Types of Optical Isomerism – Pedagogy Zone Read More »
Photolytic degradation is the degradation of photodegradable molecules caused by the absorption of photons, particularly those wavelengths found in sunlight, such as infrared radiation, visible light, and ultraviolet light. Some molecules get activated by the heat of light which increases the reaction rate. Drugs which get chemically degraded in the presence of light are photosensitive
Photolytic Degradation and its Prevention Read More »
In pharmacy, micromeritics is employed for: Release and Dissolution: Clinically, the particle size and surface area of a drug can affect its release from dosage forms administered orally, parenterally, rectally, and topically. Finely powdered drug has a high surface area, hence gets easily dissolved in dissolution fluids in vivo, thereby enhancing the drug solubility and
Pharmaceutical Applications of Micromeritics Read More »
Figure shows a schematic diagram of Coulter counter equipment used for determining the particle volume. The equipment is applicable to materials of particle size ranging between 0.5-1000μm. Principle The principle involved in the working of this instrument is that when the particles suspended in a conducting liquid passes through a small orifice (having electrodes on
Method for Determining Particle Volume Read More »
Emulsions are estimated for their flow behaviour. The flow related attributes desirable for the performance of an emulsion are: Removal of an emulsion from a bottle or tube. Flow of an emulsion through a hypodermic needle. Spreadability of an emulsion on the skin. Stress induced flow changes during manufacture (milling). Dilute emulsions possess Newtonian flow,
Rheological Properties of Emulsions Read More »
Stable emulsions can be produced by using emulsifying agents. These agents reduce the interfacial tension between the two phases and then separate the globules by creating a barrier at the interface. Surfactants are mainly used as emulsifying agents. The emulsifying agent’s solubility determines the kind of emulsion to be prepared. If using hydrophilic emulsifying agents
Emulsion Formulation by HLB Method Read More »
Emulsification is the method of dispersing a liquid in another immiscible liquid, The major groups of emulsifying agents are soaps, detergents, and compounds whose basic structure is a paraffin chain ending in a polar group. Bancroft stated that the essential conditions for a stable emulsion are that the drops of the dispersed phase should be
Theories of Emulsification – Pedagogy Zone Read More »