Phenols, Ethers, and Organic Sulfur Compound
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
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
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
Phenols - Chemical Properties
O-Na+OH
+ NaOH + HOH
Acid-Base Reactions
Phenol Sodium phenoxide
6. Complete the following reaction and name the organic reactant and product.
NaOH
+ H2O
C7H6O3NNa
OH
NO2
CH3
4-methyl-3-nitro phenol
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
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
Nomenclature of Ethers
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
F
Nomenclature of Ethers
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
Hexane, insoluble
in water
1-pentanol, slightly soluble
in water
H3CCH2
CH2CH2
CH2OH
H3CCH2
CH2CH2
CH2OH
Physical Properties of EthersThe ether oxygen can hydrogen bond with water.
The result is some water solubility.
H3CCH2
CH2CH2
OCH3
H3CCH2
CH2CH2
OCH3
1-methoxybutane, slightly soluble
in water
H3CO
CH2CH2
OCH3
H3CO
CH2CH2
OCH3
1,2-dimethoxyethane, very soluble
in water
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 ??
Related Documents
