What is meant by the following terms ? Give an example of the reaction in each case.
(i) Cyanohydrin
(ii) Acetal
(iii) Semicarbazone
(iv) Aldol
(v) Hemiacetal
(vi) Oxime
(vii) Ketal
(vii) Imine
(ix) 2,4-DNP-derivative
(x) Schiff’s base

Explanation

(I ) The compounds containing hydroxyl and cyano group on the carbon atom are called cyanohydrins these are also called gem-hydroxynitrilies . These are obtained of HCN to a carbonyl group in weeakly basic medium :
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(ii ) semicarbozones are the derivatives of aldehydes and ketons obtained by the action of semicarbazide on them in wealky acidic medium .

these are used for identification and characterization of aldehyes and ketons
( iii ) Gem- alkony alcohols are called hemiactals these are obtained by the addition of one molecule of monohydric alcohol to an aldehyde in the presence of dry HCI gas

( iv ) Gem-dialkoxy alkanes are called ketons on these compounds , the two alkoxy are present on the same carbon within the chain these are produced by the reaction of ketons with ethylene in the pressure of dry HCI gas .

these are readily hydrolysed by dilute mineral acids to regnerate the original ketons therefore ketons are used for the protections of keto groups in organic aynthesis
(ii ) 2,4-dinitrophenyl hydrozones ( 2,4 derivative are produced when aldehydes or ketons react with 2,4 dinitrophenyl hydrazine in wekly acidic medium .

(vi ) Aldols are ` beta ` - hydroxyaldehydes or ketons which are produced by the condensaton of two molecules of aldehydes or ketons containg ` alpha` - hdrogen atoms in the pressure of a dilute aqueous base .

(vii) Acetal . these are dialkoxy compounds in which two alkoxy group are present on the terminal carbon , these are product by the action of an aldehyde with two equivalents of a monohydric alcohol in the presence of dry HCI gas

( viii ) Oximea are formed when aldehydes or ketons react with hydroxyl amines in weakly acidic medium

( ix) Imines . these are the compounds containing `-CH=N-` group and are produced when aldehyes and ketons react . with ammonia derivatives

`z=-NH,-OH ,-NHC_6 - NHCHCONH_2 , ` etc
(x ) shiffs base aldehydes and ketons react with primary aliphiatic or aromatic to form azomethines which are also called schiffs base