ch2210 phenols, ethers, and organic sulfur...

CH2210 Phenols, Ethers, and

Organic Sulfur Compound

Phenols - Structure

General Structure - A “hydroxy” (OH) group attached directly to an aromatic ring:

OH OH

Phenol β-Naphtholα-Naphthol

OH

CH2 OH

Note:is not a phenol.

Phenols - Nomenclature

OH

ClBr

OH

NO2

OH

Cl

OH

Br

Br

OH

CH32-nitrophenol

or ortho-nitrophenol

3-chlorophenol or

meta-chlorophenol

4-methylphenol or

para-methylphenol

2,4-dibromophenol

4-bromo-2-chloro-5-isopropyl-phenol

Phenols are named as aromatic compounds, using the ortho-, meta-, and para- prefixes or appropriate numbering.

1 1

1

1

2

1

Phenols - Physical Properties

Low Melting Solids Soluble in Nonpolar Solvents Also, Quite soluble in Water

OH OH

OH

OH

OH

Name Phenol Catechol Resorcinol

M.P. 40.5 ºC 105 ºC 110 ºC

Solubility 8.3 g/100mL 43 g/100mL 110 g/100mL in water

Phenols - Acidity

In water, phenol dissociates slightly as a weak acid. (Another name for phenol itself is “carbolic acid”)

OH O

+ H2O + H3O +

_

Acid Base Base Acid

Phenols - Acidity

0.0001%

0.0033%

Phenols - Acidity

How acidic is Phenol? pKa = A general measure of acidity.

The lower the pKa, the stronger the acid.

Compound pKa

Methanol 16 Water 15.7 Phenol 9.9 Acetic Acid 4.8

Phosphoric Acid -2.1 Hydrochloric Acid -7

nonacids

weak acids

strong acids

Acidity of Alcohols

a very strong base

Phenols - Chemical Properties

Acid-Base Reaction:

Phenol Sodium phenoxide

or “Sodium

phenolate"

OH

OH

Na+

O

Na+

HO H+

NaOH

6. Complete the following reaction and name the organic reactant and product.

NaOH

+ H2O

C7H6O3NNa

OH

NO2

CH3

4-methyl-3-nitro phenol

sodium 4-methyl-3-nitro phenoxide

O

NO2

CH3

Na+

7. Review: What structural feature is present in some alcohols which enables the molecules to undergo intramolecular dehydration ?

8. Review: What structural feature is present in some alcohols which enables the molecules to undergo oxidation ?

9. Review: What structural feature is present in alcohols which enables the molecules to undergo a reaction with sodium (Na) metal?

10. Review: What structural feature is present in a specific class of alcohols which enables the molecule to undergo a reaction with aqueous NaOH?

C C

OHH

C

OH

H

C

OH

HOH

Phenols - Chemical Properties

OH

OH

O

O

+ 2 H .

OXIDATION

REDUCTION

O-Na+OH

+ NaOH + HOH

Acid-Base Reactions

Phenol Sodium phenoxide

Hydroquinone Paraquinone

Oxidation- Reduction Reactions

Phenols - Examples of Important Compounds

o-phenyl phenol 4-hexylresorcinol

butylated hydroxy anisole (BHA)

butylated hydroxy toluene (BHT)

OH

OH

OCH3

OH

OH

CH2CH2CH2CH2CH2CH3

OH

CH3

Structure of Ethers

Chemical Properties of Alcohols

Intermolecular Dehydration Reactions

H C C

H

H

H

O

H

H+H O C C

H

H

H

H

H

H+ + H2OH C C

H

H

H

O

H

C

H

H

C

H

H

H

C2H6O C2H6O C4H10O H2O

“H” and “OH” on two different

molecules Also called “condensation” or “dehydration synthesis”-

an extremely important reaction in biochemistry.

+ +

The reaction is run under different conditions than the

“intramolecular” dehydration.

diethyl ether2 molecules of ethanol

Nomenclature of Ethers

Common NomenclatureFor simple carbon groups, the two groups attached to the ether

oxygen are named as alkyl groups and “ether” is added to the name.

H3CCH2

OCH3

H3CCH2

OCH2

CH3

H3CCH2

O

ethyl methyl ether diethyl ether

ethyl phenyl ether


IUPAC System

Shorter carbon chains are named as “alkoxy-” groups.

CH3CH2

CHCH2

CH2Cl

OCH3

1-chloro-3-methoxypentane 2-bromo-4-ethoxy-1-fluorobenzene

H3CCH2

O

Br

F1


A compound may contain two functional groups, in which case priorities are assigned.

Important Anaesthetics

Physical Properties of EthersPhysical Properties of Ethers

Boiling points of ethers increase with molecular weight and decrease with increased branching

Physical Properties of Ethers

Attractive forces between ether molecules include only dispersion forces making their boiling points similar to alkanes of similar molecular weight.

H3CCH2

H2C

CH2H2C

CH3

H3CCH2

H2C

CH2H2C

CH3

H3CCH2

H2C

CH2H2C

CH3

H3CCH2

H2C

CH2H2C

CH3

H3CCH2

H2C

CH2H2C

CH3

Hexane, boiling point 69 °C

H3CCH2

H2C

CH2O

CH3

H3CCH2

H2C

CH2O

CH3

H3CCH2

H2C

CH2O

CH3

H3CCH2

H2C

CH2O

CH3

H3CCH2

H2C

CH2O

CH3

Butyl methyl ether, boiling point 71 °C

H3C

CH2H2C

CH2H2C

O

H3C

CH2H2C

CH2H2C

O

H3C

CH2H2C

CH2H2C

O

H3C

CH2H2C

CH2H2C

O

H3C

CH2H2C

CH2H2C

OH H H HH

1-Pentanol, boiling point 138 °C

Physical Properties of EthersThe solubility of a compound in water is related to the ability of water molecules

to overcome the attractive forces between two potential solute molecules.

H3CCH2

CH2CH2

CH2CH3

H3CCH2

CH2CH2

CH2CH3

HO

H

Hexane, insoluble

in water

1-pentanol, slightly soluble

in water

HO

H

H3CCH2

CH2CH2

CH2OH

H3CCH2

CH2CH2

CH2OH

HO

H

X

Physical Properties of EthersThe ether oxygen can hydrogen bond with water.

The result is some water solubility.

HO

H

HO

H

HO

H

1-methoxybutane, slightly soluble

in water

1,2-dimethoxyethane, very soluble

in water

H3CCH2

CH2CH2

OCH3

H3CCH2

CH2CH2

OCH3

H3CO

CH2CH2

OCH3

H3CO

CH2CH2

OCH3

HO

H

HO

H

HO

H

As a general rule, one polar atom (O,N) can “solubilize” four to six

carbon atoms.

Organic Sulfur CompoundsStructures

R-S-H Thiols (Mercaptans)

R-S-R Thioethers (Sulfides)

R-S-S-R (Disulfides)

Nomenclature

CH3-S-H Mercaptan (Methanethiol)

CH3-S-CH3 Dimethyl Sulfide (Dimethyl Thioether)

CH3-S-S-CH3 Dimethyl disulfide

Physical Properties

Distinct odors and flavors

Lower boiling points than alcohols (Why?)

Weak Acids: Phenols > Thiols > Alcohols

Thiols are easily “oxidized” to disulfides and

Disulfides are easily “reduced” to thiols.

Organic Sulfur Compounds Chemical Properties

H-SS-H

SS

Oxidation

Reduction

This reaction takes place within large protein structures:

Mercaptans = “Mercury capturing”

R-SH R-S

Hg2+ Hg + 2 H+

R-SH R-S

Process is called “chelation”

Organic Sulfur Compounds Chemical Properties

Where Do We Find Thiols ??

Where Do We Find Disulfides ??

Stereochemistry - Review of Isomerism

Stereoisomers

Isomers

Structural Isomers

Stereochemistry - Review of Isomerism

Isomers

Structural Isomers Stereoisomers

Isomers with chiral centers

Cis-trans Isomers

Stereochemistry - “Handedness” in Everyday Objects

We can imagine the mirror image of an object.

In some cases, the mirror image and the original object are identical. In some cases, the mirror image and

the original object are not identical.

Stereochemistry - “Handedness” in Everyday Objects

Stereochemistry - “Handedness” in Organic Compounds

Enantiomers - compounds that have the following characteristics:

1) Molecules of two compounds are mirror images of each other.

2) Molecules of two compounds are nonsuperimposable.

The characteristics of enantiomers are often the

result of a single “chiral” carbon atom.

Stereochemistry

All tetrahedral carbons are not chiral.

Stereochemistry - A Chiral Tetrahedral Carbon

1, 2, 3, and 4 must be different groups. What are “different” groups?

Stereochemistry - Examples of Enantiomers

bromochlorofluoromethane


2-bromobutane


L-carvone D-carvone

Chiral Compounds - Biological Activity

CH

HCl C Br

Cl

HCBr

HH C H

Cl

H

CH3CH2CH2CHClCH3

H3C CH2CH2 C CH3

H

Cl

CH

HOH

CH

OHCH

OHCHO

OH

CH3CH2CHCH2CH3

CH

HOH

CH

OHCH

CO

OHCH

OHCHH

OHHO C

HCO

HCNH2

HOH

H3C CH2 C CH2 CH3

H

OH

a) b) c)

d) e)

f)g)

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