organic compounds containing oxygen, halogen, or sulfur

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