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    صيدله

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    شاهيد كابور



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    تاريخ التسجيل : 28/08/2008

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    حصري صيدله

    مُساهمة من طرف شاهيد كابور في الأربعاء مارس 03, 2010 1:21 am



    what is tautomerism?


    Existence of two or more chemical compounds that have the same chemical composition but different structures (isomers) and that convert easily from one to another. A major class of tautomeric reactions involves exchange of a hydrogen atom between two other atoms in the same molecule, in both cases forming a covalent bond. For example, in keto-enol tautomerism, the hydrogen atom bonded to the carbon atom in a carbonyl (keto) group (
    -CH-C=O; see functional group) moves to the oxygen atom, making it an enol group (-C=C-OH). The keto form predominates in many aldehydes and ketones, the enol form in phenols. sugars (e.g., glucos) exhibit tautomerism between open (chain) forms and closed (ring) forms. See also isomerism



    oxime`s definition


    An oxime is one in a class of chemical compounds with the general formula R1R2 C=NOH, where R1 is an organic side chain and R2 is either hydrogen



    Any of a group of compounds formed by treating aldehydes or ketones with a nitrogen-containing reducing agent
    .







    preparation of oximes


    Oximes can be synthesized by condensation of an aldehyde or a ketone with hydroxylamine. The condensation of aldehydes with hydroxylamine gives aldoxime, and ketoxime is produced from ketones and hydroxylamine. Generally, oximes exist as colorless crystals and are poorly soluble in water. Therefore, oximes can be used for the identification of ketone or aldehyde.

    Oximes can also be obtained from reaction of nitrites such as isoamyl nitrite with compounds containing an acidic hydrogen atom. Examples are the reaction of ethyl acetoacetate and sodium
    nitrite in acetic acid, the reaction of methyl ethyl ketone with ethyl nitrite in hydrochloric acid. and a similar reaction with propiophenone,the reaction of , the reaction of phenacyl chloride with sodium nitrite in acetic acid

    A conceptually related reaction is the japp-klingemann
    reaction.





    Nitroso


    Nitroso
    refers to a functional group in organic chemistry which has the general formula RNO. Nitroso compounds are a class of organic compounds containing the nitroso functional group, R−N=O.





    oxime nitroso tautomerism


    the form of the tautomerism is in the following




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      الوقت/التاريخ الآن هو السبت نوفمبر 18, 2017 3:59 pm