8/13/2019 Alknes Tips
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ALKENES OR OLEFINS
* General formula of olefins is c"H2n.* Functional grou resent
i! # $ #%& 'no(n as olefinic or et)lenic grou.
* l+,e formula of olefms R-#H $ #H.
* #ommon name/Alkylene 0 I1,A# name isAlkene.
* )e fIrst mem3er of al'ene series is #H4& #H $ #H&
'no(n as et)lene or et)ene.
H H
* In 5c $ #% 6i5 # $ # 3on7 7istance is 894A& 6iI5 # $ #
f:n7 energ is 89; 'cal mole-tH H
* 6ill5 $ #-H 3on7 7istance is 8.8OA& $ #-0-H 3on7 energ is
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8/13/2019 Alknes Tips
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-'7""'-""
* R...,CH = CHz > CHz = CHz > CHz = CH-X(X = CI, Br or
I).* Alkenes generally sho !os#on, $han, rng-$han an%geo&e#r$al
so&ers&.* I-B#ene (CHs) an% -B#ene (CHs) are !os#on
so&ers.* Alkenes (CnHn) are n$#onal so&er$ #h
$y$loalkanes(CnHn)' e.g., !ro!ene
(CH+-CH = CHz, C) s so&er$ #h $y$lo!ro!ane (C).* I-Alkenes
%o o# sho geo&e#r$al so&ers& # -Alkenes
%eIn#ely e/h# cis-trans so&ers&. * Alkenes o #y!e Cab =
Cab,Cab = Cae an% Cab = Cae sho geo&e#r$al so&ers&.
* An alkyne $an e hy%rogena#e% #o an alkene y using
0n%lar$a#alys# (1%ClBa23)'
1%* R-C == C-R 4 Hz ... $s-Alkene.
(0n%lar catlllst5
Na CliD NlI9
* R-# $$ #-R H . trans-al'ene.* Alkenes $an e !re!are% y
el&na#on rea$#ons s$h as%ehy%rohalogena#on o alkyl hal%es
an% #hese el&na#on rea$#ons ollo Saytzeff's rnle.
* A$$or%ng to Saytzeff's nIle, #he hy%rogen a#o& s
el&na#e% ro& #ha#+-$aron a#o& h$h has
leas# n&er o hy%rogen atoms. * )e reagents generall use7
for
7e)7ro)alogenation are alc. KOH or NaNH liD NH9. * )e
reacti>it of al'l )ali7es to(ar7s
7e)7ro)alogenation follo(s t)e or7er/
R-I R-r R-#I R-F.
88% !enes f1e forme7 3 7e)7ration of alco)ols. )e common
7e)7rating agents use7 areHSO4 conc.PzOs, H9,O4& AlO9&
)O& ncl& etc.
* Electrolsis of so7ium or otassium salts of succinic aci7 in
concentrate7 aDueous solution gi>es
et).lene !t ano7e.* Alkenes are slig)tl @e! >D@atile t)an
al'!es an7 melting oint as (ell as 3oiling oints of
al'enes
are slig)tl )ig3er t)an t)ose of correson7ing al'anes.
* De to t)e resence of al'l grou 6R5 is R-#H $ #H& al'enes
un7ergo su3stitution reactionsan7 7ue to t)e resence of # $ # %
3on7& t)ese s)o( a77ition reactions. &
* ecause of unsaturation or # $ # % grou& al'enes are more
reacti>e t)an al'anes. Al'enes
generall gi>e electro)ilic a77ition reactions at t)e
n-3on7.
* Halogens a77 on al'enes gi>ing >icinal 7i)aloal'anes.* A
;B solution of r in ##! is use7 as a test of unsaturation in
organic comoun7s.
* Organic comoun7s containing # $ # % an7or -# $$ #- 3on7
7ecolorie r in ##!.
* Electro)ilic a77ition on al'enes is trans a77ition.* Rea$#5#y
o hy%rogen hal%es to(ar7s an al'ene follo(s t)e or7er H/I Hr
H#I HF.
* A77ition of hy%rogen )ali7es to an unsmmetrical. al'ene ta'es
lace in accor7ance (it)
ar'o(ni'offs rule0 an7 a77ition ta'es lace >ia t)e formation
of a more sta3le car3onium ion.
