review organic chemistry chemistry 203. goal of atoms filled valence level noble gases (stable)...

Review

Organic Chemistry

Chemistry 203

Goal of atoms Filled valence levelNoble gases

(Stable)

Bonding

1. Ionic bonds

2. Covalent bonds

Ionic bonds

result from the transfer of electrons from one element to another.

Bonding

Metals: lose 1, 2 or 3 e- Cation (Y+)

Nonmetals: gain 1, 2 or 3 e- Anion (X-)

Ions

Cation (Y+): Na+ Li+ Ca2+ Al3+

Anion (X-): Cl- F- O2-

Bonding

Ionic bonds

Metal-Nonmetal

Na: 1s2 2s2 2p6 3s1 Cl: 1s2 2s2 2p6 3s2 3p5

AnionCation

Na+: 1s2 2s2 2p6 Cl-: 1s2 2s2 2p6 3s2 3p6

Ne Ar

Bonding

Covalent bonds

result from the sharing of electrons between two atoms.

Nonmetal-NonmetalMetalloid-Nonmetal

Sharing ofvalence electrons

Lewis Dot Structure

H He Li CAl N Cl

H H Or H H

Or Cl H

Lewis Structure

HCl

Cl: 1s2 2s2 2p6 3s2 3p5

H: 1s1 He: 1s2

Ar: 1s2 2s2 2p6 3s2 3p6

Intermolecular Forces

London dispersion forces

Dipole-dipole interaction

Hydrogen bonding

Ionic bondsCovalent bonds<

Intramolecular (Bonding) Forces



Attractive forces between all molecules

Only forces between nonpolar covalent molecules

2+

No PolarityOriginal Temporary

Dipole

δ- δ+

+2+

HeHe

Original Temporary Dipole

Induced Temporary Dipole

__ _ _

He He

2+_ ___ 2+

δ- δ+He

__ 2+

δ- δ+He

__ 2+


T ↓ Kinetic energy ↓Move slower

Attractive forcesbecome more important liquid

He: T = -240°C (1 atm) → liquid

Dipole-Dipole Interactions

Attractive forces between two polar molecules

stronger than London dispersion forces

boiling point ↑

Hydrogen bonding

Between H bonded to O, N, or F (high electronegativity) → δ+and a nearby O, N, or F → δ-

Stronger than dipole-dipole interactions & London dispersion forces

H2O

H O

H

H

O

H

- +

hydrogenbond

hydrogenbond

- +

(a) (b) (c)

Hydrogen bonding

CH3COOH

Acetic acidδ-

δ+

H-bonding in our body

DNA

H-bond

Protein (α-helix)

H-bond

Solubility

polar dissolves polar

Nonpolar dissolves nonpolarlike dissolves like

octane CCl4octane + CCl4

Organic Compounds

Hydrocarbons

Large family of organic compounds

Composed of only carbon and hydrogen

Saturated hydrocarbons

Alkanes

Unsaturated hydrocarbons

Alkenes, Alkynes & Aromatics

C - C C = C C CC

CC

C

CC

H

H

H

H

H

H

A Kekulé structureshowing all atoms

A Kekulé structureas a line-angle formula

Alkanes

Chemical reactions of Alkanes

Low reactivity

1- Combustion:

• Alkanes react with oxygen.

• CO2, H2O, and energy are produced.

• Alkane + O2 CO2 + H2O + heat

CH4 + 2O2 CO2 + 2H2O + energy

2- Halogenation:

Alkanes react with Halogens.

CH4 + Cl2 CH3Cl + HCl

Heat or light

Chemical reactions of Alkanes

Low reactivity

CH3Cl+ Cl2 CH2Cl2 + HCl

CH2Cl2+ Cl2 CHCl3 + HCl

CHCl3+ Cl2 CCl4 + HCl

Heat or light

Heat or light

Heat or light

Chloromethane

Dichloromethane

Trichloromethane

Tetrachloromethane

Alkenes & Alkyens

Chemical properties of Alkenes & Alkynes

More reactive than Alkanes

Addition of Hydrogen (Hydrogenation-Reduction)

Addition of Hydrogen Halides (Hydrohalogenation)

Addition of water (Hydration)

Addition of Bromine & Chlorine (Halogenation)


Addition reactions

Exothermic reactions

–C = C – – C – C–

Products are more stable (have the lower energy).

• A hydrogen atom adds to each carbon atom of a double bond.

• A catalyst such as platinum or palladium is used (Transition metals).

H H H H

│ │ Pt │ │

H–C=C–H + H2 H– C – C– H

│ │

H H

Ethene Ethane

1. Hydrogenation (Reduction):

Pt

More reactive than Alkanes


• A hydrogen halide (HCl, HBr, or HI) adds to alkene to

give haloalkane.

H H H H

│ │ │ │

H–C=C–H + HCl H– C – C– H

│ │

H Cl

Ethene Chloroethane

2. Hydrohalogenation:More reactive than Alkanes


2. Hydrohalogenation:

- reaction is regioselective.

- Markovnikov’s rule: H adds to double bonded carbon that has the greater number of H and halogen adds to the other carbon.

CH3CH=CH2 HCl CH3CH-CH2

HClCH3CH-CH2

ClH

1-Chloropropane(not formed)

2-ChloropropanePropene

+

The rich get richer!


3. Hydration (addition of water):

• Water adds to C=C to give an alcohol.

• Acid catalyst (concentrated sulfuric acid).

• A regioselective reaction (Markovnikov’s rule).

CH3CH=CH2 H2OH2SO4

CH3CH-CH2

HOH

Propene 2-Propanol+

CH3C=CH2

CH3

H2OH2SO4 CH3C-CH2

CH3

HO H2-Methyl-2-propanol2-Methylpropene

+


• A halogen atom adds to each carbon atom of a double bond.

• Usually by using an inert solvent like CH2Cl2.

H H H H

│ │ │ │

CH3–C=C–CH3 + Cl2 CH3– C – C– CH3

│ │

Cl Cl

2-Butene 2,3-dichlorobutane

4. Halogenation:

CH2Cl2

More reactives than Alkanes


Aromatic Hydrocarbons

Halogenation

Nitration

Sulfonation

No addition reactions (almost unreactive)

Chemical properties of aromatics

Aromatic substitution: One of the H atoms is repalecd by some groups.

Chemical properties of benzene

1. Halogenation:

H Cl2FeCl3 Cl HCl+ +

ChlorobenzeneBenzene

Cl and Br react rapidly with benzene in the presence of an iron catalyst.

2. Nitration:

H HNO3H2SO4

NO2 H2O++

Nitrobenzene


In presence of concentrated nitric acid and sulfuric acid, one of the H atoms is replaced by a nitro (-NO2) group.

3. Sulfonation:


H H2SO4 SO3H H2O+

Benzenesulfonic acid

+

In presence of concentrated sulfuric acid and heat, one of the H atoms is replaced by sufonic acid (-SO3H)

group.

Heat

OH NaOHH2O

O-Na+ H2O+

Phenol Sodium phenoxide(a water-soluble salt)

+OH

Alcohols

Chemical Properties of Alcohols

1. Acidity of Alcohols:

2. Acid-Catalyzed Dehydration:

CH3CH2OH CH2 = CH2 + H2OH2SO4

180°C

3. Oxidation of Alcohols:

C = C + H20Dehydration

Hydration- C – C -

H OH

OH NaOHH2O

O-Na+ H2O+

Phenol Sodium phenoxide(a water-soluble salt)

+

Alkene having the greater number of alkyl groups on the double bond

generally predominates.

Acid-Catalyzed Dehydration

CH3CH2CHCH3

OH H3PO4 CH3CH=CHCH3 CH3CH2CH=CH2

1-Butene (20%)

2-Butene (80%)

2-Butanol

+-H2O

CH3CHCHCH3OH

CH3 H2SO4CH3C=CHCH3

CH3

CH3CHCH=CH2

CH3

3-Methyl-1-butene2-Methyl-2-butene (major product)

3-Methyl-2-butanol

+-H2O

In the oxidation [O] of a primary alcohol 1, one H isremoved from the –OH group and another H from the Cbonded to the –OH.

primary alcohol aldehyde

OH O │ ║ CH3─C─H CH3─C─H + H2O │ H

ethanol ethanal (ethyl alcohol) (acetaldehyde)

Oxidation of 1° Alcohols

K2Cr2O7

H2SO4

[O]

The oxidation of 2 alcohols is similar to 1°, except that a

ketone is formed.

secondary alcohol ketone

OH O │ ║

CH3─C─CH3 CH3─C─CH3 + H2O │

H

2-propanol 2-propanone


[O]

K2Cr2O7

H2SO4

Tertiary 3 alcohols cannot be oxidized.

Tertiary alcohol no reaction

OH │

CH3─C─CH3 no product │

CH3 no H on the C-OH to oxidize

2-methyl-2-propanol


K2Cr2O7

H2SO4

[O]

Thiols

Chemical Properties of Thiols

1. Thiols are weak acids (react with strong bases).

CH3CH2SH + NaOH CH3CH2S-Na+ + H2OH2O

2. Oxidation to disulfides: -S-S- disulfide

2HOCH3CH2SH + O2 HOCH2CH2S-SCH2CH2OHOxidation

Reduction

Sodium ethanethiolate

CH3-NH2 CH3-NH-CH3

CH2CH3 CH3 CH=CH2

TolueneEthylbenzene Styrene

NH2

Amines

Chemical properties of Amines

They are weak bases (like ammonia): react with acids.

N

H

H

CH3 .. + H – O – H....N

H

H

CH3 H+

O – H......

-

(to form water-soluble salts)

(CH3CH2)2NH HCl

NCH3COOH

NH

(CH3CH2)2NH2+Cl-

CH3COO-

Diethylammoniumchloride

+Pyridinium acetate

+(a)

(b) +

Aldehydes & Ketones

Chemical properties of Aldehydes and Ketones

1. Oxidation: only for aldehydes (not for ketones).

K2Cr2O7

H2SO4

CH3─CH2─CH2─CH2─C─OH

=

O

CH3─CH2─CH2─CH2─C─H

=

O

Pentanal Pentanoic acidK2Cr2O7: Oxidizing agent

CH

O

Benzoic acidBenzaldehyde

+ O2

COH

O

2 2Liquid aldehydes

are sensetive to oxidation.

No oxidizing agent


2. Reduction:

Like reducing the alkene (C = C) to alkane (C – C):

– Reduction of an aldehyde gives a primary alcohol (-CH2OH).

– Reduction of a ketone gives a secondary alcohol (-CHOH-).

H2

tran sition

metal catalyst+

1-Pen tan ol

CH3─CH2─CH2─CH2─C─ H

=

O

PentanalCH3─CH2─CH2─CH2─CH2─ OH

H2

tran si tion

metal cataly st+CH3─C─CH2─CH3

=

O

CH3─CH─CH2─CH3

-OH

2-butanol2-butanone

3. Addition of alcohols (hemiacetals):

CH

OO-CH2CH3

HC OCH2CH3

H

O-H+

Benzaldehyde Ethanol A hemiacetal

H of the alcohol adds to the carbonyl oxygen and

OR adds to the carbonyl carbon.

unstable



O-CH2CH3H C OCH2CH3

H

O CH2CH3

+

Ethanol An Acetal

C OCH2CH3

H

O-H

A hemiacetal

+H2OAcid

3. Addition of alcohols (Acetals):

H

O

O-HC

O O

H

H

O O-H

H

4-Hydroxypentanal A cyclic hemiacetal

123

45

1345

redraw to show the -OH and -CHO close

to each other2

3. Addition of alcohols (hemiacetals):

If –OH is part of the same molecule that contains C=O.


Carboxylic Acids

carbonyl group O

CH3 — C—OH hydroxyl

Carboxyl group

COOH NaOHH2O

COO- Na

+H2O+ +

Benzoic acid(slightly soluble in water)

Sodium benzoate(60 g/100 mL water)

COOH NH3H2O

COO- NH4

++

Ammonium benzoate(20 g/100 mL water)

Benzoic acid(slightly soluble in water)

1- Reaction with bases:

Chemical properties of Carboxylic Acids

2- Reduction:


Resistant to reduction

Using a powerful reducing agent: LiAlH4 (Lithium aluminum hydride).

1° alcohol

COH

=OLiAlH4, ether

H2OCH2OH

3-cyclopentene-carboxylic acid

4-Hydroxymethyl-cyclopentene


3- Fischer Esterification:

- A carboxylic acid reacts with an alcohols to form an ester.

- Using an acid catalyst such as concentrated sulfuric acid.

CH3C-OHO

H-OCH2CH3

H2SO4CH3COCH2CH3

OH2O

Ethanoic acid(Acetic acid)

++

Ethyl ethanoate(Ethyl acetate)

Ethanol(Ethyl alcohol)

The best way to prepare an ester.

4- Decarboxylation:


Loss of CO2 from a carboxyl group.

decarboxylation +O

RCOH RH CO2Heat

Esters & Amides

CH3 — C — NH2

O

Amide group

Formation of Esters

RCOHO

A carboxylic acid

=

Fischer Esterification

RCOR'O

RC-OHO

H- O R '

==

An alcoholA carboxylic acid An ester

H2SO4

+ H2O

Chemical Reactions of Esters

1. Hydrolysis: reaction with water.

(breaking a bond and adding the elements of water)

RCOR 'O

RC-OHO

H- O R '

= =An alcoholA carboxylic acidAn ester

+ H2O +Heat

Acid

2. Saponification (Hydrolysis): an ester reacts with a hot aqueous base.

RCOR'O

RCO-NaO

H- O R '

= =

An alcoholA sodium saltAn ester

+ NaOH +H2O

Heat - +

CH3COCH2CH3

OCO-NaO

CH3CH2OH

= =EthanolSodium acetateEthyl Ethanoate

+ NaOH +- +

CH3


3. Esters react with ammonia and with 1° and 2° amines to form amides.

Thus, an amide can be prepared from a carboxylic acid by first converting the carboxylic acid to an ester by Fischer esterification and then reaction of the ester with an amine.

OCH2CH3

O

+ NH3 NH2

O

+ CH3CH2OH

Ethyl 2-phenyl acetate 2-Phenylacetamide


Formation of Amides

RCOHO

A carboxylic acid

=

RCNHR'O

RC-OHO

H- N HR

==

An AmineA carboxylic acid An amide

Heat+ H2O'

H2OCH3C-NHCH2CH3

OHHNCH2CH3CH3C-OH

O+ +

Acetic acid Ethanamine N-ethylethanamide

Chemical Reactions of Amides

Such as esters:

Hydrolysis in hot aqueous acid or base.

CH3CH2CH2CNH2

OH2O HCl

H2OCH3CH2CH2COH

ONH4

+Cl

-

Butanoic acidButanamide

++ +heat

CH3CNHO

NaOHH2O

CH3CO-Na+O

H2N

AnilineSodiumacetate

Acetanilide

++heat

Amides do not react with ammonia or with amines.

Chemical Reactions of Amides

review organic chemistry chemistry 203. goal of atoms filled valence level noble gases (stable)...

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