organic compounds containing oxygen, halogen, or sulfur
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Organic Compounds containing Oxygen, Halogen,
or Sulfur
Alcohols, Ethers, Alkyl Halides & Thiols
• ROH• ROR• RX• RSH
• All of these compounds contain a carbon atom that is singly bonded to a heteroatom (other than H or C)!
• Alcohols & ethers can be considered organic derivatives of water
• Replacing H(s) with one or two alkyl groups• HOH; ROH; ROR
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
• IUPAC1. 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
• CH3CH2CH2OH 1-propanol
• CH3CHCH3
|
OH 2-propanol
3,4-dimethylcyclohexanol
• Alcohols with >1 -OH groups• Ex.: CH2CH2
| | 1,2-ethanediol
OH OH
l
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
• Common• Methyl alcohol• Ethyl alcohol• Isopropyl alcohol• Ethylene glycol• Propylene glycol• Glycerol (glycerin)
For survival in northern winters, many fish and insects produce large amounts of glycerol that dissolve in their blood, thereby lowering the freezing point.
How does % relate to “proof”?
Constitutional Isomerism
• Positional• Ex.: butanol 1-butanol
2-butanol
• Skeletal• Ex.: butanol 2-butanol sec-butyl alcohol
2-methyl-2-propanol tert-butyl alcohol
Physical Properties of Alcohols• Alcohols have both Polar & Nonpolar character!
(-OH) (alkyl)• Properties are determined by which portion dominates
• Short chain (<6) - polar end dominates• Long chain (6+) - nonpolar end dominates
• BP increases with increasing # of C atoms• Effect of London Dispersion Forces
• Water solubility• Short chain - soluble• Long chain - insoluble
• Alcohols can Hydrogen bond • (better with small chain alcohols)• affects BP & Solubility in Water
• Alkanes cannot Hydrogen bond
• (a) The polar hydroxyl functional group dominates the physical properties of methanol.
• (b) Conversely, the nonpolar portion of 1- octanol dominates its physical properties.
Chemical Reactions of Alcohols
• Combustion• CH3OH + O2 --> CO2 + H2O
• Two types of Dehydration!• Intramolecular Alcohol dehydration
• Conditions: 180˚C and H2SO4 catalyst• Result: formation of alkene (elimination/condensation rxn)• Ex.: C-C-OH ----> C=C + H2O• Ex.: 2-butanol -->
• Zaitsev’s rule: major product
is alkene w/ greatest # of alkyl groups
Chemical Reactions of Alcohols
• Intermolecular Alcohol dehydration• Conditions: 140˚C (lower temp!) and H2SO4
catalyst• Result: formation of ether (R-O-R)
(condensation rxn)
• Ex.: C-OH + HO-C ----> C-O-C + H2O
Halogenation Reactions
• R-C-OH + X2 ----> R-C-X2 + H2O
• Not a particularly common reaction, however
Oxidation Reactions
• Oxidation results in an increase in the number of C-O bonds or a decrease in the number of C-H bonds.
• 1˚ alcohol ---> aldehyde ---> carboxylic acid
• 2˚ alcohol ---> ketone
• 3˚ alcohol ---> No Reaction!
Th
e oxid
ation of e
tha
nol
is the b
asis for the
“bre
athalyze
r test.”
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”.
• Ex.:
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)
Occurance & 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
Ma
ny com
me
rcially
bake
d go
ods co
ntain
the
antioxida
nts B
HA
a
nd B
HT
to he
lp p
revent spo
ilag
e.
Nutmeg tree fruit. A phenolic compound, isoeugenol, is responsible for the odor associated with nutmeg.
Ethers
• Structural Characteristics• Functional group = -C-O-C-
• Remember ascorbic acid?
• R-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
• Ex.: C-C-O-C-C-C-C
• Common• Name the two alkyl
groups (alpha order) attached to the O and add the word “ether”.
Examples:
Isomerism
• Consitutional• Partitioning of C
atoms (by O) - positional!
• Isomers of individual alkyl groups
• Ex.: C4 ethers
• Functional Group Isomers (1st time we encounter this possibility)
• 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
• Act as anesthetics• Diethyl ether
• Chemical• Flammable
• React w/ O2 to form unstable (explosive) ccompounds
• Unreactive w/ acids and oxidizing agents
• Halogenation• Prepared by intermolecular
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 explosion
The 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.)
Space-filling models of the four ethyl halides.
Do these molecules act as polar or non-polar?
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
Safe, non-toxic,
non-flammable
alternative to
dangerous
substances
(e.g. ammonia)
for aerosol-spray
propellants,
refrigerants,
solvents, and
foam-blowing agents
CFCs and refrigeration
CFCs and propellants
UV radiation in the stratosphere
The Ozone Layer Chemistry
CFCl3 + UV LightUV Light ==> CFCl2 + Cl Cl + O3 ==> ClO + O2
ClO + O ==> Cl + O2
The chlorine free radical atomis then able to attack anotherozone 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!
The ozone destruction process requires conditions cold enough (-80oC) for stratospheric clouds to form.
Once these stratospheric clouds form the process can take place, even in warmer conditions
Ozone consumption has been greatly reduced,
1997 ozone
hole
2003 ozone
hole
however CFCs may linger for another 150 years in the atmosphere
Ozone layer thickness
Thiols = Mercaptans: sulfhydryl group (-SH) bonded to a saturated C atom
• Alcohol - R-OH• C-C-OH (ethanol)• (ethyl alcohol)
• Thiol - R-SH• C-C-SH (ethanethiol)• (ethyl mercaptan)
Properties of Thiols
• Physical• Low BP
• No H-bonding
• Strong odor• Skunks (3-methyl-1-
butanethiol)
• Methanethiol (additive to natural gas)
• Morning breath• Onions (1-propanethiol)
• Chemical• Oxidation-Reduction2 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 sulfideMethanethiolDimethyl sulfide…
• Onions • GarlicDisulfides are
important in some protein structures.
What do you need to know?• Structural characteristics (know the functional group)
• Alcohol• Phenol• Ether• 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
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