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Write formula and name about alkyl groups |
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Answer» Solution :(A) In branched chain hydrocarbons the alkyl group present as a branch. Alkyl groups (-R): The removed of one hydrogen atom from the molecule of an alkane GIVES an alkyl group. `underset("alkane")(R- H) overset(-H)rarr underset("alkyl group")(-R)` Nomenclature (Ane + AYL = Alkyl) this SMALL alkyl groups are in branced chain hydrocarbons: In a branched chain compound small chains of carbon ATOMS are attached at one or more carbon atoms of hte parent chain. The small carbon chains (branches) are called alkyl groups: For example: (i) `CH_(3) - underset(underset(CH_(3))(|))(CH) - CH_(2) - CH_(3)` In four carbon containing parent chain, the `-CH_(3)` (Methyl) alkyl group is in branch. (ii) `CH_(3) - underset(underset(CH_(2)CH_(3))(|))(CH) - CH_(2) - overset(overset(CH_(3))(|))(CH) - CH_(3)` In five carbon containing parent chain the `-CH_(3) and -CH_(2)CH_(3)` groups in branch. (B) Nomenclature of alkyl group: In order to name such compounds,the name of alkyl groups are prefixed to the name of parent alkane. General formula alkyl group: `C_(n) H_(2n + 1)` Name of alkyl group : (Ane + yl) = Alkyl. One H is less in alkyl group than correspond in alkane.  The branch and unbranch structures of propyl, butyl and pentyl are as following. (a) Structure and name of propyl: `C_(3)H_(7)` (i) `underset("n- propyl")(CH_(3) CH_(2) CH_(2))`- (ii) `underset("isopropyl")(CH_(3) - underset(underset(CH_(3))(|))(CH)-)` (b) Structure and name of butyl: `C_(4)H_(9)` (i) `underset("n -butyl")(CH_(3) - CH_(2) - CH_(2) - CH_(2)-)` (ii) `underset("isobutyl")(CH_(3) - underset(underset(CH_(3))(|))(CH) - CH_(2) -)` (iii) Secondary butyl: `CH_(3) - CH_(2) - overset(|)(C )H - CH_(3) OR CH_(3) - CH_(2) - underset(underset(CH_(3))(|))(CH) -` (c ) Structure and names of pentyl: `C_(5)H_(11)` (i) `underset("n-pentyl")(CH_(3) - CH_(2) - CH_(2) - CH_(2) - CH_(2) -)` (ii) Second pentyl: `{:(CH_(3)- CH- CH_(2)- CH_(2) - CH_(3)),("|"),(CH_(3) - CH_(2)- CH_(2) - CH-),("|"),(""CH_(3)):}` OR `{:(CH_(3)- CH_(2) - CH- CH_(2) - CH_(3)),("|"),(CH_(3)CH_(2)- CH- ),("|"),(""CH_(2)CH_(3)):}` (iii) Isopentyl `CH_(3) - underset(underset(CH_(3))(|))(CH) - CH_(2) - CH_(2)- OR (CH_(3))_(2) CH CH_(2) CH_(2)-` (iv) Neopentyl `CH_(3) - underset(underset(CH_(3))(|))overset(overset(CH_(3))(|))(C ) - CH_(2) - OR (CH_(3))_(3) C- CH_(2) -` |
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