Download Organic Chemistry - Unit 2

Functional Groups
There are many different families or classes of organic compounds. The thing that differentiates
them is a functional group. The functional group is a specific arrangement of atoms that is
capable of characteristic chemical reactions. The double and triple bonds are considered
functional groups as they are reactive.
Families of Organic Compounds
Substituted Hydrocarbons
substituted hydrocarbons – these are hydrocarbons where at least 1 hydrogen is replaced with
some other atom or group of atoms. (substituents)
halocarbon – this is a hydrocarbon containing a halogen substituent.
alkyl halide – this is an aliphatic hydrocarbon containing halogen substituents.
aryl halide – this is a halocarbon in which there is a halogen substituent on an arene ring.
(Substituted benzene)
In all of these compounds, the halogen is considered to be the functional group.
Very few halocarbons exist in nature but they are easily produced in substitution reactions.
Alcohols
Alcohol – an organic compound containing at least one hydroxyl group. ( – OH ) group. The
hydroxyl is the functional group.
General formula -R
OH
Naming alcohols
1. alcohols have the same name as the corresponding alkane but the ending of the PC is “ ol “.
2. If there is more than 1 hydroxyl, indicate this with a prefix. ie. 2 - diol
3 - triol
3. Indicate the position of the hydroxyl(s) if need be.
4. An aromatic alcohol is called a “phenol” or “hydroxybenzene”
H
H
C
OH
H
methanol
H
H
H
C
C
H
H
ethanol
OH
H
H
H
H
C
C
C
HO
H
OH
H
1,3-propanediol
propane-1,3-diol
Characteristics
Alcohols boil at higher temp. than other hydrocarbons of comparable mass. This is due to the
fact that the hydroxyl group forms hydrogen bonds.
Short chain alcohols are soluble in water because they form hydrogen bonds with water
molecules. Long chain alcohols are good solvents for non-polar substances.
Alcohols are used as starting materials for many other organic compounds.
H
Common Alcohols
H C OH
1. methanol – CH3OH
H
 Called wood alcohol
 Very poisonous (causes blindness in small amounts)
 Readily absorbed through the skin
 Used as a paint solvent
H H
2. ethanol – C2H5OH
H C C OH
H H
 Called grain alcohol
 Made by the fermentation of sugars
 It is a solvent in lacquers, varnishes, perfumes and flavourings.
3. propanols – C3H7OH
H H H
H H H
H C C C H
H C C C OH
H O H
H
H H H
1-propanol (propyl alcohol)
brake fluid
2-propanol (isopropyl alcohol, isopropanol)
rubbing alcohol
4. butanols – C4H9OH
H
H
H
H
H
H
H
C
C
C
C
H
O
H
H
H
H
H
H
2-butanol
sec-buty alcohol
C
H
C
H
C
H
H
OH
C
OH
H
C
H
H
C
H
C
H
C
H
H
H
H
H
2-methyl-1-propanol
isobutanol
isobutyl alcohol
2-methyl-2-propanol
tert-butyl alcohol
5. polyalcohols (glycols)
H
HO
H
C
C
H
H
OH
1,2-ethanediol
ethylene glycol
antifreeze
H
H
H
H
C
C
C
O
H
O
H
O
H
H
1,2,3-propanetriol
glycerine
glycerol
Alcohol Elimination Reaction
Alcohols undergo elimination reactions to produce alkenes. This type of reaction involves
concentrated sulphuric acid as a catalyst to remove a hydrogen atom and a hydroxyl group to
produce water.
H
OH
H
C
C
H
H
H
acid
H
C
H
H
H
ethane
+
C
ethene
O
H
H
water
Aldehydes and Ketones
Both of these families contain the same functional group. The functional group is called a
carbonyl. ( - CO)
In aldehydes, the carbonyl is attached to the end of the PC. In a ketone, it is anywhere but on the
end.
General Formulas
O
O
R
R
C H
C R
ketone
aldehyde
Naming Aldehydes and Ketones
1. Aldehydes are named by taking off the “e” on the ending of the PC’s name and adding an
“al”.
2. Do the same thing for ketones but the ending is “one” .
3. Pick the longest chain with the carbonyl(s) and number the chain so the carbonyl(s) get the
lowest total.
4. A benzene ring with a carbonyl attached is called “benzaldehyde”.
Characteristics
Aldehydes
 Short chain aldehydes have sharp, irritating odors.
 Larger ones have flowery odors and are diluted to make perfumes.
O
methanal (formaldehyde)
H
C H
 strong odor
 used as a starting material in the production of some plastics.
 at one time it was used for preserving biological specimens. (not used anymore because it
is a carcinogen)
O H
C C H
H
ethanal (acetaldehyde)
H
 primarily used in the production of other organic compounds. ie. acetic acid
Ketones
Propanone (acetone)
 Used as a solvent in nail polish removers, , plastic cements, resins and varnishes.
 It is sold as a cleaner.
* Aldehydes and ketones can be distinguished by using a Fehling’s solution. (Cu 2+ ions)
Aldehydes turn it from blue to red and ketones have no affect on it.
Carboxylic Acids
This family of compounds contain a functional group called a carboxyl. ( - COOH)
It is made up of a carbonyl and a hydroxyl.
General formula
O
R
C OH
Naming Carboxylic Acids
1. Take the “e” off of the PC and add “oic acid”.
2. The carbon on the carboxyl group is given the lowest number.
3. If there is more than one carboxyl, a prefix is put in front of the “oic acid” ie. dioic acid
Characteristics
 Found in fruits and other foods with sour, tangy taste.
 Molecules are polar and form hydrogen bonds with each other and water molecules.
 Smaller molecules (1-4 carbons) are miscible in water.
 Larger ones are basically immiscible.
 Litmus distinguishes these compounds from other hydrocarbon derivatives.
O
methanoic acid (formic acid)
H
C OH
 used to remove hair from animal hides, recycling rubber and as a preservative and
antibacterial agent in livestock feed.
H
ethanoic acid (acetic acid)
H C
O
C OH
H
 Acetic acid is a mainly used in the production of other organic compounds.
 Acetic acid gives vinegar its sour taste but the amount used in is comparatively small.
H H H
H
O
H
C
H H
O
H C C C C
OH
H
H
C
H
H
H
H C C C C
OH
H H H
H
propanoic acid
2,3-dimethylbutanoic acid
Reactions of Carboxylic Acids
condensation reaction – the reaction of a carboxylic acid and another reactant (alcohol) to
produce water and another organic compound. (ester)
esterification – carboxylic acid + alcohol
ie.
H H H
+
H C C C C
HO C C H
OH
O
H C C C C
H H H
H H
butanoic acid
water
H H H
H H
O
H H H
ester +
ethanol
O
H H
C C H
H H
+
O
H
H
ethylbutanoate
water
Condenses out
Esters
The functional group is similar to that of a carboxylic acid, but the H has been replaced with a
hydrocarbon branch.
O
General formula
C
R
O
R
Naming Esters
1. Name the parent chain as the portion that came from the carboxylic acid, but change the
ending from “oic acid” to “oate”.
2. Treat the alkyl group from the alcohol as the attached group.
H H
H
+
C C C
H H
HO C
OH
H
H
methanol
H
H
H
H
C
C
C
C
H
H
H
H
O
H
H
H
C
C
C
H
H
H
O
H
C
H
methylpropanoate
O
C
O
C C C
H H
H
propanoic acid
H
H H
H
O
H
propylpentanoate
H
+
O
H
H
water
H
H
H
H
C
H
H
Br H
C
C
C
C
C
H
H
F
H
H
O
C
O
H
H
H
C
C
C
isobutyl-3-bromo-4-fluoro-5-methylhexanoate
H
H C H
H H H
Characteristics
 Most have a pleasant, fruity odor (found naturally in many plants)
 Often added to foods to enhance smell and taste.
 Also used in cosmetics, synthetic fibers and solvents.
Amides
O
Amides have a functional group consisting
of a carbonyl attached to a nitrogen.
R
C
R
N
R
Amides are formed in a condensation reaction between a carboxylic acid and an amine.
Naming Amides
1. Change the name of the carboxylic acid reactant from “oic acid” to “amide”.
2. Amides with substituents on the nitrogen have their names preceded by an “N”.
O
O
ie.
CH3
C
C
NH2
CH3
NH
CH2
CH2
CH3
ethanamide
N-propylethanamide
Amides can be produced in a condensation reaction.
O
CH3 CH2 C
O
H
+
H3C CH2 C
H N
OH
H
NH2
+
O
H
H
Condenses out
propanoic acid
ammonia
propanamide
water
Characteristics
 Amide functional groups occur in proteins.
 They are the peptide bonds that join the amino acids that make up the proteins.
Amines
Amines consist of one or more alkyl groups attached to a nitrogen atom. This functional group
is called an amino group. R
N
General formula
R
R
Synthesizing Organic Compounds
Polymers
Polymerization – the formation of very large molecules from small molecular units.(monomers)
Polymers have long existed in nature but have only been synthesized in the 20 th century.
They can have molar masses in millions of grams/mol.
There are 2 basic types of polymers.
Addition polymers – these polymers are created by addition reactions.
Many plastics are produced by the polymerization of alkenes.
ie. polyethylene – this is an extremely long alkane molecule formed by the addition reaction of
the monomer “ethylene”. It is called polyethylene because it is the molecule created by
bonding many ethylene molecules together.
Another polymer created in this manner is polytetrafluoroethene or teflon