Chapter 14 - Organic Compounds containing Oxygen, Halogen or Sulfur
Alcohols, Ethers, Alkyl halides & Thiols
ROH
RX
ROR
RSH
All of these compounds contain a carbon atom that is singly bonded to a
heteroatom!
Alcohols & ethers are organic derivatives of water
- Replacing H with one or two alkyl groups
Alcohols
Structural Characteristics
R-OH -OH (hydroxyl = functional group)
-OH is bonded to a saturated C atom!
Classification
Primary (1˚)
C-C-OH
Secondary (2˚)
C-C-OH
|
C
Tertiary (3˚)
C
|
C-C-OH
|
C
Alcohol Nomenclature
IUPAC
1.Name the longest chain (drop the “e” and add “ol” at the end) to which OH is attached.
2.# the chain from the end nearest the -OH (# the position of the -OH
group).
3.Name/locate any substituents.
4.For rings, -OH is on C#1.
IUPAC naming examples
Ex.: CH3OH
Methanol
CH3CHCH3
|
2-propanol
OH
3,4-dimethylcyclohexanol
•Alcohols with >1 -OH groups
Ex.: CH2CH2
| |
OH OH
1,2-ethanediol
Alcohol Nomenclature
Common (name “R” as an alkyl group)
Alkyl group name + alcohol
Ex.: CH3OH
Methyl alcohol
CH3CHCH3
|
Isopropyl alcohol
OH
•Alcohols with >1 -OH groups
•Ex.:
Important Common Alcohols
IUPAC
Methanol
Ethanol
2-propanol
1,2-ethanediol
1,2-propanediol
1,2,3-propanetriol
Constitutional Isomerism
Positional
Ex.: butanol
•Skeletal
•Ex.: butanol
Common
•Methyl alcohol
•Ethyl alcohol
•Isopropyl alcohol
•Ethylene glycol
•Propylene glycol
•Glycerol (glycerin)
1-butanol
2-butanol
2-butanol
sec-butanol
2-methyl-2-propanol
tert-butanol
Physical Properties of Alcohols
Alcohols have both Polar (-OH) & Nonpolar (alkyl) character!
Properties are determined by which portion dominates
- Short chain - polar end dominates: The polar hydroxyl functional
group dominates the physical properties of methanol.
- Long chain - nonpolar end dominates: Conversely, the nonpolar
portion of 1- octanol dominates its physical properties.
BP
increases with increasing # of C atoms
of London Dispersion Forces
Water solubility
Short chain - soluble
Long chain - insoluble
Alcohols can Hydrogen bond
(better with small chain alcohols)
Alkanes cannot Hydrogen bond
Effect
Chemical Reactions of Alcohols
Combustion
CH3OH + O2 -->
CO2 +
H2O
Intramolecular Alcohol dehydration
Conditions: 180˚C and H2SO4 catalyst
Result: formation of alkene
Ex.: C-C-OH ----> C=C + H2O
Intermolecular Alcohol dehydration
Conditions: 140˚C
Result: formation of ether (R-O-R)
Ex.: C-OH + HO-C ----> C-O-C + H2O
Halogenation Reactions
R-C-OH + X2 ----> R-C-X2 + H2O
Oxidation Reactions
Carbon atoms are oxidized if they lose H or gain O.
Carbon atoms are reduced if they gain H or lose O.
1˚ alcohol ---> aldehyde ---> carboxylic acid
2˚ alcohol ---> ketone
3˚ alcohol ---> No Reaction!
Preparation of Alcohols
Alcohols can be prepared in two major ways:
Alkene hydration
Ex.: CH2=CH2 + H2O ----> CH3CH2OH
Addition of H2 to a carbonyl group ( C=O)
Ex.: Aldehyde + H2 ----> 1˚ alcohol
Ketone + H2 ----> 2˚ alcohol
Phenols
Structural Characteristics
-OH is attached to a C that is part of an aromatic ring.
Ar-OH
Nomenclature of Phenols
Phenol = “phenyl” + “alcohol”
IUPAC rules are same as for benzene derivatives. Parent ring is “phenol”.
Physical & Chemical Properties of Phenols
Flammable, like alcohols
Phenols cannot be dehydrated.
Oxidation occurs only with strong oxidizing agents.
Halogenation
Weak acids in solution (Ka~10-10)
Occurrence & Uses of Phenols
Antiseptics (but phenol derivatives are much safer than phenol itself).
Mouthwashes, Lysol, etc.
Antioxidant - several phenols are preferentially oxidized
Food additives
Vit. E
Flavoring agents
Irritants: poison ivy & poison oak
Ethers
Structural Characteristics
Functional group = -C-O-CR-O-R
R-O-R’
R-O-Ar
Ar-O-Ar
Nomenclature of Ethers
IUPAC
Select longest C chain = base name.
Change -yl ending of other group to -oxy. (ie. Methyl becomes
methoxy)
Place alkoxy name (w/ locator #) in front of base chain name
Common
Name the two alkyl groups attached to the O and add the word
“ether”.
Isomerism
Consitutional: partitioning of C atoms (by O)
Isomers of individual alkyl groups
Ex.: C4 ethers
Functional Group Isomers: consitutional isomers with different
functional groups
Ex.: C3 ether and C3 alcohol
Physical & Chemical Properties
Physical
BP = to alkanes; lower than alcohols
No H-bonding w/ self possible
Water soluble: can H-bond w/ water
NP substances are generally soluble in ethers
Chemical
Flammable
React w/ O2 to form unstable (explosive) ccompounds
Unreactive w/ acids and oxidizing agents
Halogenation
Prepared by intermolcular dehydration of 1˚ alcohols
Alkyl Halides:
Incoming halogen atom (orange sphere) replaces a hydrogen atom in the alkane
model.
Naming:
Treat halogen atoms like alkyl groups.
F = fluoro; Cl = chloro; Br = bromo; I = iodo
Ex.: CH3-CHBr-CHBr-CHI-CH2-CH3
Halogenation Reactions
General equation: RH + X2 → RX + HX
Hydrocarbon + Halogen  Halogenated + acid
(diatomic) hydrocarbon
Ex.
CH4 + Cl2 -->
CH3Cl + HCl
Highly exothermic reaction: can lead to an explosionThe process can
continue to alter the resulting products as long as the halogen remains in
sufficient quantities to drive further reactions. (The halogen would be the
__________ reactant.)
Chlorofluorocarbons (CFCs)
Developed in the 1930's
Very stable compounds composed of C, F, Cl, & H
Freon is the tradename:
Trichlorofluoromethane
Dichlorodifluoromethane
Trichloro-trifluoroethane
Dichloro-tetrfluoroethane
Chloropentafluoroethane
The Ozone Layer Chemistry
CFCl3 + UV Light ==> CFCl2 + Cl
Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2
The chlorine free radical atom is then able to attack another ozone molecule
Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2
and again ...
Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2
and again... thousands of times!
A catalyst!
Thiols = Mercaptans: sulfhydryl group (-SH) bonded to a saturated C atom
Alcohol - R-OH
C-C-OH (ethanol) or (ethyl alcohol)
Thiol - R-SH
C-C-SH (ethanethiol) or (ethyl mercaptan)
Properties of Thiols
Physical
Low BP: no H-bonding
Strong odor: Skunks, Methanethiol (additive to natural gas),
Morning breath
Chemical
Oxidation-Reduction
2 thiols <==> Disulfide
Important in Protein chemistry
Thioethers - replace the “O” with “S” (R-S-R)
C-S-C
C-S-C-C-C
Ar-S-C
C=C-S-C
C=C-C-S-C
C=C-C-S-S-C-C=C
Morning Breath = Hydrogen sulfide. Methanethiol, Dimethyl sulfide…
Onions
Garlic
What do you need to know?
Structural characteristics (know the functional group)
Alcohol
Phenol
Ether
Alkyl halides
Sulfur Analogs
Isomers
Nomenclature (the rules for naming the molecules)
Common & IUPAC
Physical properties (basic/simple)
BP; Solubility; Flammability
Occurrence and uses (common)
Natural (ex.: menthol, skunk, nutmeg, clove, garlic, onion)
Synthetic (ex.: antiseptics, racing fuel, de-icers, antioxidants, anesthetics)
Preparation (what basic reactions produce the molecules)
Alcohols - alkene hydration; Phenols - benzene hydration
Ethers - intermolecular alcohol dehydration
Characteristic reactions of the molecules
Combustion; dehydration*; halogenation; oxidation
