Strc Effects& Acid Base Prop Part 1
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S tructural & A cid-Base
Roldan M. de Guia Department of Biochemistry Faculty of Pharmacy University of Santo Tomas
Structural Effects ele ct ron d eloca li zati on CH2
.. NH2
.. : CH Cl ..
.. : Cl ..
.. O .. C .. NH2
:O: CH3
C
.. O .. H
Structural Effects
electron delocalization (Resonance)
Structural Effects
electron delocalization (Resonance)
Structural Effects
electron delocalization (Resonance)
:O:
.. :O
H
.. :O: N+
:O: C H
.. NH2
Structural Effects
Hyp ercon jugat io n
H H C CH CH2 H H
+
..-
H C CH CH2 H
H
..+ H C CH CH2 H
H
..H C CH CH2 H
+
Structural Effects
Hyperconjugation
Dienes
CH2
CH CH CH2 conjugated
isolated
cumulative
Structural Effects
Hyperconjugation
H
H
H C H
H C H
H H C H
+
-
+
..
.. -
Structural Effects
Hyperconjugation H
O
H C C H
O
H
+
H O H C C H H
O
Structural Effects +
CH3
+
CH3
CH3
+
CH2
CH2 H3C
H -
:CH3
-
O2N
C: H H
. CH
3
C. H
C
+
CH3
Structural Effects
Induct ive Eff ect
Ele ct ron at tr ac ti ng in duc ti ve with excess positive charges +
+
R N R
NH3
+
NO2
R those with electronegative atoms NH2
OH
F
OCH3
Cl Br groups exhibiting orbital electronegativity C N
N N
those with easily polarizable valence electrons I
-
Structural Effects
Induct ive Eff ect
Ele ct ron at tr ac ti ng in duc ti ve δ+
δ−
H3C Cl δ+
δ++
δ−
CH3
CH2
Cl
CH3
CH3 +
H3C N CH3 --
δ+ CH2
δ− O
H
δ+
Structural Effects
Induct ive Eff ect
Ele ct ron re pe lling i nd uct ive effec t
alkyl groups CH3
negative groups -
COO
O H3C C
--
O
S
H3C
-
-
O
S
-
H3C CH C N H3C
Structural Effects
St eric Ef fe ct
Structural Effects
Hyd ro gen B ond ing + F
H δ
O
H δ+
N
R
O
H δ+
F
H
δ+
O
H
δ+
N
H
δ+
H
O
O H
F
O H O
H O H H
H O R
R C
H
C R O H O
H C O O H
OH
OH
Acids and Bases
Brønsted–Lowry Acids and Bases • An acid is a proton donor • A base is a proton acceptor
acid
base
base
acid
Note that water can act as an acid or a base
Acids and Bases
Brønsted–Lowry Acids and Bases
acid
base
conjugate base
conjugate acid
Every acid–base reaction involving proton transfer has two conjugate acid–base pairs.
Acids and Bases
Lewis Acids and Bases • A Lewis acid is an electron pair (think empty orbital) acceptor.
A Lewis base is an electron pair (think filled orbital) donor. The result of a Lewis acid–base reaction is often called an adduct.
Roldan M. de Guia Department of Biochemistry Faculty of Pharmacy University of Santo Tomas
Structural Effects ele ct ron d eloca li zati on CH2
.. NH2
.. : CH Cl ..
.. : Cl ..
.. O .. C .. NH2
:O: CH3
C
.. O .. H
Structural Effects
electron delocalization (Resonance)
Structural Effects
electron delocalization (Resonance)
Structural Effects
electron delocalization (Resonance)
:O:
.. :O
H
.. :O: N+
:O: C H
.. NH2
Structural Effects
Hyp ercon jugat io n
H H C CH CH2 H H
+
..-
H C CH CH2 H
H
..+ H C CH CH2 H
H
..H C CH CH2 H
+
Structural Effects
Hyperconjugation
Dienes
CH2
CH CH CH2 conjugated
isolated
cumulative
Structural Effects
Hyperconjugation
H
H
H C H
H C H
H H C H
+
-
+
..
.. -
Structural Effects
Hyperconjugation H
O
H C C H
O
H
+
H O H C C H H
O
Structural Effects +
CH3
+
CH3
CH3
+
CH2
CH2 H3C
H -
:CH3
-
O2N
C: H H
. CH
3
C. H
C
+
CH3
Structural Effects
Induct ive Eff ect
Ele ct ron at tr ac ti ng in duc ti ve with excess positive charges +
+
R N R
NH3
+
NO2
R those with electronegative atoms NH2
OH
F
OCH3
Cl Br groups exhibiting orbital electronegativity C N
N N
those with easily polarizable valence electrons I
-
Structural Effects
Induct ive Eff ect
Ele ct ron at tr ac ti ng in duc ti ve δ+
δ−
H3C Cl δ+
δ++
δ−
CH3
CH2
Cl
CH3
CH3 +
H3C N CH3 --
δ+ CH2
δ− O
H
δ+
Structural Effects
Induct ive Eff ect
Ele ct ron re pe lling i nd uct ive effec t
alkyl groups CH3
negative groups -
COO
O H3C C
--
O
S
H3C
-
-
O
S
-
H3C CH C N H3C
Structural Effects
St eric Ef fe ct
Structural Effects
Hyd ro gen B ond ing + F
H δ
O
H δ+
N
R
O
H δ+
F
H
δ+
O
H
δ+
N
H
δ+
H
O
O H
F
O H O
H O H H
H O R
R C
H
C R O H O
H C O O H
OH
OH
Acids and Bases
Brønsted–Lowry Acids and Bases • An acid is a proton donor • A base is a proton acceptor
acid
base
base
acid
Note that water can act as an acid or a base
Acids and Bases
Brønsted–Lowry Acids and Bases
acid
base
conjugate base
conjugate acid
Every acid–base reaction involving proton transfer has two conjugate acid–base pairs.
Acids and Bases
Lewis Acids and Bases • A Lewis acid is an electron pair (think empty orbital) acceptor.
A Lewis base is an electron pair (think filled orbital) donor. The result of a Lewis acid–base reaction is often called an adduct.
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