Organic and Biochemistry

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Development of Complex Curricula for Molecular Bionics and Infobionics Programs within a consortial* framework**

Consortium leader

PETER PAZMANY CATHOLIC UNIVERSITY

Consortium members

SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER

The Project has been realised with the support of the European Union and has been co-financed by the European Social Fund ***

PETER PAZMANY CATHOLIC UNIVERSITY SEMMELWEIS

UNIVERSITY

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Functional groups: their unique role

(Funkciós csoportok: Különleges szerepben)

Organic and Biochemistry

(Szerves és Biokémia )

semmelweis-egyetem.hu

Compiled by dr. Péter Mátyus

with contribution by dr. Gábor Krajsovszky

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> >

^O

c) Type of hybridization

HC CH H₂C CH₂ H₃C CH₃ pK_a ~ 25 pK_a ~ 43 pK_a ~ 48

C_sp > C_sp² > C_sp³

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a) through

- covalent bonds (σ és π) - field

b) Designation:

(the arrow indicates its direction)

c) Diminishing with distance

δ+ δ- H₂C Cl H₃δC+> >>

>

Inductive effect:

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d) Two directions:

negative (-I):

toward the more electronegative substituent;

e.g. -OH, -X, -NH₂, -COOH, etc;

positive (+I):

toward carbonatom

e.g. alkyl group, metals, carboxilate group

δ+ δ- H₂C Cl H₃Cδ+> >>

C R

O R < C <

M R <

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2. Mesomeric effect (conj., resonance):

By a group attached to an unsaturated system and possessing an unshaired pair of electrons, resulting in a new electron distribution.

More than one Lewis structures. Positive or negative

Conditions required: - coplanarity of interacting groups

- parallel arrangement of overlapping orbitals

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Types of conjugation:

1. π - π :

- Generally –M

N N > C N > ^C

O

>

N O

O ^C > >

O

O R

C O

NR₂

C O

O

S O

O OH

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H₂C CH CH CH₂ H₂C CH CH CH₂ H₂C CH CH CH₂

H₂C CH CH O H₂C CH CH O H₂C CH CH O

O O O

O O

δ- δ+

Cyclic examples:

Acyclic examples:

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2. n - π :

- Generally +M

C> OH C> OH -I

+K

-I

+K F > ^Cl > ^Br > ^I

~ >

> ^OH

O OR O C

O R

>

NR₂

NH₂ ~ ^{NH C}

O R

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O O

O O H₂C CH CH₂ H₂C CH CH₂

H₂C CH NH H₂C CH NH

H₂C CH O H₂C CH O

Acyclic examples: Cyclic examples:

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3. σ - π :

Particularly in case of carbocations

C C C

HH H

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3. Field effect:

Through space

Example 2.

OH O

H OH

O H

H

H Cl

Cl

COOH

Cl

Cl H

H

COOH

pK_a = 6,07 pK_a = 5,67

pK = 2,00 pK = 3,03

Example 1.

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Substituent I M

-H 0,00 0,00

-F -0,74 +0,60

-Cl -0,72 +0,24

-Br -0,72 +0,18

-I -0,65 +0,12

-CH₃ +0,01 +0,41

-CF₃ -0,64 -0,76

-0,25 +0,37

-OH -0,46 +1,89

-OCH₃ -0,54 +1,68

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Substituent I M

-NH₂ -0,38 +2,52

-N(CH₃)₃ -0,69 +3,81

-NHCOCH₃ -0,77 +1,43

-COCH₃ -0,50 -0,90

-COOH, -COOEt -0,44 -0,66

-CN -0,90 -0,71

-COO^- +0,27 -0,40

-NO₂ -1,00 -1,00

-⁺N≡N -2,36 -2,81

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Aromatic electrophylic subst (S_EAr) : orientation rules

Substituent Effect Orientation

-O^- +I, +M Activation

Deactivation

Ortho,para

meta -NH₂, -NHR, -NR₂

-I < +M -OH, -OR

-NHCOR -OCOR

alkyl +I,

aryl +M

-F, -Cl, -Br, -I -I > +M -CONH₂, -CONHR, -CONR₂

-I, -M -COOH, -COOR

-CHO, -COR

-SO₃H, -SO₂NH₂, -SO₃R -C≡N

-NO₂ -(N≡N)⁺

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Steric effect:

Steric hindrance

Example

N

H C CH₃ O

N H

S OH

O O

C CH₃ O

HOSO₂Cl

acetanilide 4-acetilamino-benzenesulfonic acid

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Steric effect:

Steric acceleration

Example

N O

NH₂

CH₂ N

O NH₂

CH₂

SO₂O

SO₂O SO₂O

no desulfonation was observed reductive desulfonation

SO₂O

OO₂S

Organic and Biochemistry

Functional groups: their unique role

Organic and Biochemistry

Compiled by dr. Péter Mátyus

with contribution by dr. Gábor Krajsovszky

Table of Contents

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>

Steric effect:

Steric hindrance

Steric effect:

Steric acceleration