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Showing posts from October, 2008

ALKALOID

An alkaloid is any of a class of nitrogen-containing natural product of plant origin that have an alkaline, or basic, chemical nature. Some alkaloid are simple, monocyclic (one-ring) amines (see cyclic compounds), but many are very complex, polycyclic amines. Occurrence More than 200 alkoloids are known. They are present in only about 10 to 15 % of all vascular plants . Often found in the dicotyledone group of the angiosperm, or flowering plants, they seldom occur in monocotyledone or in other plant groups, such as gymnosperms. The most actively growing parts of such plants usually contain the highest percentage of the compounds. Among the more familiar alkaloid are aconitine (From monkshood), atropine (from belladonna), codeine, morphine, and papaverine (from opium poppy), nicotine (From tobacco) quinidine and quinine (from cinchona bark), solanine (from potate and tomato), ricinine (from castor bean) and strychnine and brucine (from Nux fomica). Function. Why certain plants

Chemical Ionic Bond

A chemical bond is formed when separate atoms are brought together and the sharing or transfer of electrons occurs. Chemical bonds can be weak or strong, depending on the nature of the interactions. The chemical bond itself happen cause by a chemical reaction between atom. The physical and chemical properties of most compounds are due, in large part, to these bonding forces. Ionic Bonding When two or more atoms combine, a competition for the available electrons can occur that leads to a nearly complete transfer of one or more electrons. The resulting formation of an ionic bond involves the removal of an electron from one atom, a process known as ionization potential of the atom. The other atom gains an electron, and the measure of its ability to do so is known as its electron affinity. An ionic bond result from the strong electrostatic forces of attraction between the negatively charged anions and positively charged cations. When atoms of sodium and chlorine are brought together,

Chemical Reaction Rate

From an engineering viewpoint, reaction kinetics has these principal functions: Establishing the chemical mechanism of a reaction obtaining experimental rate data Correlating rate data by equations or other means; Designing suitable reactors, Specifying operating conditions, control methods, and auxiliary equipment to meet the technological and economic needs of the reaction process . The discussion of Chemical reaction rate will different if seen from different background science. Reactions can be classified in several ways. On the basis of mechanism they may be: 1. Irreversible 2. Reversible 3. Simultaneous 4. Consecutive A further classification from the point of view of mechanism is with respect to the number of molecules participating in the reaction, the molecularity: 1. Unimolecular 2. Bimolecular and higher Related to the preceding is the classification with respect to order. In the power law rate equation r = k(Ca)p. (Cb)q, the exponent to which any particular r

Tools of Chemistry

Chemistry is a precise laboratory science, and the equipment of a chemical laboratory is usually involved with measurement. Balances are used to measure mass, pipettes and burettes to measure volume, and thermometers to measure temperature changes. Advances in electronics and computer technology have enabled the development of scientific instruments that determine the chemical properties, structure, and content of substances accurately and precisely. Most modern chemical instrumentation has three primary components; a source of energy, a sample compartment within which a substance is subjected to the energy, and some sort of detector to determine the effect of the energy on the sample. An X-ray diffractometer, for instance, enables the chemist to determine the arrangement of atoms, ions, and molecules that constitute crystals by means of scattering X-rays. Most modern laboratories contain ultraviolet, visible, and infrared spectrophotometers, which use light of various wavelengths