12-14 reverse, Flashcards
halogenation of OH by HX
O grabs H from H-X, becomes -OH2+
second step X- replaces OH2+
Overall its an a transformation adding X to C
HX
X=Cl, Br, I
Halogenation of alcohol
OH replaced by Cl
SOCl2
also requires mild base, poor nucleophile
Halogenation of OH
OH replaced by Br
PBr3
requires mild base, poor nucleophile
Sn2
LG leaves ( Cl, Br, I, OT)
nucleophile comes on, reagent replaces LG
switches enantiomers (R to S or vis)
SN2 Good Nucleophile ( strong base) Br, Cl, I
LG out replaced by OH
enantiomers switch
Sn2
NaOH or KOH
LG leaves replaced by OR
Sn2
NaOR (Na+ OR-)
R-C (triple bond )C-H replace H with another group ex R-C triplebond C to r-C TB C-CH2-R
1)strong base NaNH2
2) R-CH2-LG
LG = Cl, Br, I, Ts
alkyl halide (r-X) or tosylate (R-OTs) to alkene good leaving group comes off along with H (x and H) double bond forms C=C can form both E and Z
E1
weak base
ethanol (or polar protic solvent ( has Hs on N,O,X))
Heat
E1
allylic or benzyllic OH to alkene
OH is secondary or tertiary
OH and H come off
C=C forms between two C’s
acid (H2SO4 or H3PO4)
Heat
1 step no carbo cation
methyl leaving group or no carbocations or beta-H’s
has to be methyl, primary, secondary or 1* w/ allylic/benzyllic LG
not tertiary
Good nuclei-strong base-cool
or Good nuk-weak-aprotic
SN2
2 Steps carbo forms,
Only secondary or Tert or 1* if allylic/benzyllic LG
Good nuke-weak base- polar protic ( h on NOX)
or
Poor nuk-weak base or polar protic solvent-cool
Sn1
1 Step no carbo forms
1, 2, 3*
strong base, poor nuk, hot
E2
2 Step, carbo forms
1* if allylic or benzyylic LG, 2, 3
WEAK Base only, usually hot,
poor nun, weak base (protic solvent), Hot
E1