Chapter
3 ROH, ArOH, ROR’ , RSH
| Some Compounds with
Oxygen, Sulfur, or a Halogen -- Slides by Warren Gallagher at the University of Wisconsin, Eau Claire http://www.chem.uwec.edu/Chem150_S06/Pages/lecture-materials.html > Lecture 3 |
| Alcohols, ethers, and
thiols by Gary Trammell and Srinivas Vuppuluri at the University of Illinois at Springfield http://people.uis.edu/gtram1/organic/alcoholsmenu.htm |
This chapter is our first real
exposure to non-hydrocarbon organic compounds, other than haloalkanes,
and centers on compounds containing
oxygen singly bonded to carbon; the
three classes of compounds can be viewed as
organic derivatives of water in
which one
(alcohols, ROH and phenols, ArOH)
or both
(ethers, R-O-R’)
hydrogens have been replaced by alkyl or aryl groups. These
compounds are of great industrial, economic, and biological importance. Since sulfur
is directly below oxygen in the periodic
table, we will also look at
thiols (RSH) and
disulfides (RS-SR’), compounds of
extreme biological significance. Finally, we will begin to examine
multifunctional compounds,
those which simultaneously belong to more than one class.
I. ALCOHOLS (Sect
3.1 to 3.5)
A. Structure:
contain a hydroxyl group attached to carbon
B. Nomenclature:
replace the -e in the stem name with -ol; CH3OH is methanol;
Number the longest chain containing the -OH group
in such a way that the hydroxyl
group gets the lowest number. e.g., (CH3)2CHCH2CH2CHOHCH2CH3
is
6-methyl-3-heptanol, not
2-methyl-5-heptanol.
(See table of
alcohols for
examples)
See Dave Woodcock’s Chime structures of alcohols at OUC at
http://www.molecularmodels.ca/molecule/Alcohols.htm
1. Primary: the OH-bearing C is directly connected to only one other C (e.g.,
1-pentanol)
methanol is considered to be
a “special case”
2. Secondary: the OH-bearing C is directly attached to two other carbons (e.g.,
isopropanol)
3. Tertiary: the OH-bearing C carries three other carbons (e.g.,
2-methyl-2-butanol)
D. Physical properties
[see Fig. 3.2,
3.6, and 3.3, 3.4, and 3.5]
1. Solubility in H2O:
C1 toC3: miscible; C4 to C6:
soluble; >C6; insoluble
2. Melting and boiling points much higher than corresponding alkanes
(H-bonding)
3. Soluble in other alcohols, ether, acetone, etc.
E. Reactions
[see “Study Skills 3.1”, p. 85]
1. Dehydration (with sulfuric acid)
a. Intramolecular:
yields alkenes
3o > 2o > 1o
b. Intermolecular:
yields ethers
c. Biological examples
2. Oxidation [review the three definitions]
a. Complete = combustion;
low-m.w. burn with blue (clean) flame;.gasohol
b. Partial: with oxidizing agents like CrVI, ( or NAD+
in biological systems)
1o (RCH2OH)----à
aldehydes (RCHO)---à carboxylic acids(RCO2H)
`
2o (R2CHOH) ---------à
ketones
(R2C=O)
3o
(R3COH)
no reaction
F. Uses: solvents, starting materials, cosmetics, antifreeze
see
table 3.2, p 88
II. PHENOLS (Sect
3.6) have the –OH
group directly
attached to an aromatic ring
A. Examples and nomenclature
B. Properties/ uses: disinfectants
and antioxidants
See
Dave Woodcock’s Chime structures of phenols at OUC at
http://www.molecularmodels.ca/molecule/Phenols.htm
A. Structure and nomenclature: identify and name the groups flanking the
Oxygen
B. Properties and uses
less polar than alcohols, more polar than hydrocarbons : make
good solvents
highly flammable; otherwise, not too
reactive: ∴
make good solvents
diethyl ether: the original general anesthetic
See
Dave Woodcock’s Chime structures of ethers at OUC at
http://www.molecularmodels.ca/molecule/Ethers.htm
A. Nomenclature: 3-methyl-1-butanethiol
(CH3)2CHCH2CH2SH
is “essence of skunk”
B. Interconversion by redox: 2RSH
+ [O] à
RS-SR; RS-SR + [H] à
2 RSH
C. Biological significance: protein
structure & enzyme action; affinity
for heavy metals
To
learn more about the chemistry of
skunk spray, see William F. Wood’s
site at Humboldt State University
http://www.humboldt.edu/~wfw2/chemofskunkspray.html
A very few examples that we have seen:
cholesterol
[polycyclic, alkene, alcohol]
cysteine
[thiol, amine, carboxylic acid]
THC
[phenol, polycyclic, ether]