Yogy's biology

10. HALOGEN DERIVATIVES - part 07 - Reaction with active metals Reaction with active metals : Active metals like  sodium, magnesium,cadmium  readily combine with  alkyl chlorides, bromides and iodides  to form compounds containing  carbon-metal bonds.  These are known as  organometallic compounds. a. Reaction with magnesium :  When alkyl halide is treated with  magnesium in dry ether  as solvent, it gives  alkyl magnesium halide.  It is known as  Grignard reagent. Grignard reagents are very reactive compounds.  They react with  water  or compounds containing  hydrogen attached to electronegative element . b. Wurtz reaction :  Alkyl halides react with  metallic sodium in dry ether  as solvent, and form  higher alkanes containing double the number of carbon atoms present in alkyl halide. This reaction is called  Wurtz reaction.  When a mixture of two different alkyl halides is used, all the  three possible alkanes  are formed. Do you know ? Carbon-magnesium bond in Grignard reagent is a 

07 Plant Growth and Mineral Nutrition - part 17 - Nitrogen cycle Nitrogen cycle:  It is series of natural processes by which  Nitrogen enters successively from air to organisms through soil and back to environment.  Plants use photosynthetic product, the  sugars to make proteins.  To do this, they need nitrogen.  Unfortunately, it is very  innert  (nonreactive). Plants need nitrogen in a reactive form usually as  nitrate ions. Nitrogen is a  limiting nutrient  in the agricultural ecosystems.  It exists as nitrogen atoms with a strong triple covalent bond  (N≡N).  A regular supply of nitrogen to the plants is maintained through biological and physical process.  Nitrogen fixation : Atmosphere is the source of nitrogen.  Can not be used directly.  Combines with  C, H, N and O  to form compounds before being used. Conversion of  free nitrogen (N 2 )  of the atmosphere into nitrogenous salts to make it available for the plants, is called  nitrogen fixation.  Types of Nitrogen fixation : Phy

07 Plant Growth and Mineral Nutrition - part 16 - Mineral nutrition Mineral nutrition :  Minerals constitute most commonly  -  Occuring solid Inorganic materials obtained from the earth's crust.  Plant absorbs mineral elements from surroundings (soil, air and water) for its use.  About  36 to 40  different elements of periodic table are used as minerals by the plants.  These are absorbed in ionic (dissolved) form as  PO 4  , CO 3  , SO 4   , etc.,usually through roots ( regions of elongation and growth ).  Sources of minerals :  Carbon  enters the plant as  atmospheric carbon-dioxide.  Source of  hydrogen  is  water  and  oxygen  comes from  air and water.  Carbon, Hydrogen and oxygen are not minerals in origin.  Source of  nitrogen  is the  soil.  Plant derives nitrogen from both mineral and non-mineral origin.  Classificaion of minerals :  1. Classificaion of minerals [ on the basis of their requirement minerals]  :   - Essential and  Non-essential.  1. Essential minerals :  Thos