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Transcript
Organic Chemistry
Functional Groups
• The hydrocarbon skeleton of an organic
molecule is chemically inert.
• Most organic chemistry, then, involves the
atoms and molecules that are attached to
this main chain.
• Functional groups are the atoms in an organic
compound that have been added to a
hydrocarbon chain. They are the only part of
the molecule that is capable of reacting
chemically.
• Compounds are classified according to their
functional groups. Since these groups can be
attached to any chain, we will represent the
inert hydrocarbon chain with “R”.
• The presence of a functional group has a
major effect on the physical properties of a
compound.
• Intermolecular forces determine many
physical properties, such as solubility and
boiling point:
• hydrocarbons – have only weak dispersion
forces.
• functional groups – may have strong
hydrogen bonds.
Hydrogen Bonding
• Boiling Points: Compounds with hydrogen bonding
have higher than expected boiling points: at SATP,
C2H6 = gas but CH3OH = liquid.
• Solubilities: Compounds with hydrogen bonds are
usually soluble in water (a polar molecule): C6H14 =
insoluble in water but C5H11OH = soluble in water.
• Solubility decreases, as the molecule gets longer.
(C12H25OH =slightly soluble in water).
– This is because the hydrogen bonding –OH group has less
effect on the larger molecule.
Halocarbons
• Halocarbons are produced by the
substitution of a halogen (Family VIIA) for
hydrogen in the hydrocarbon chain
Cl = chloro Br = bromo I = Iodo F = Fluoro
NO2 = nitro NH2 = amino
• The halocarbon is treated as a substituent.
• Don’t forget that substituents are named
alphabetically.
• CH3-C(Br)(CH3)-CH3
2-bromo-2-methylpropane
• CH3-CH(Cl)-C(NO2)(C2H5)-CH2-CH3
2-chloro-3-ethyl-3-nitropentane
Practice
• Name or provide the formula for the
following:
a) CH3-CH2(I)
b) CH2(Cl)-CH2(Cl)
c) CH(F)(F)-CH(Cl)(Cl)
d) CH3-CH2-CC-CH2(NH2)
e) CH3-CH(NO2)-CH2(Br)
f) trichloromethane
g) 2-chloro-3-iodo-1-butene
h) 1,5-dinitro-2-pentyne
i) 1,3-difluorocyclopentane
j) 1,3-dibromo-3-phenylhexane
Alcohols
• Alcohols contain the hydroxyl (-OH) group:
R–O–H
• Nomenclature: Add “-ol” to the stem of the
name of the parent chain. Number the
position of the hydroxyl group.
• If more than one –OH group is present, use
these endings:
a)“-diol” (two hydroxyls)
b) “-triol” (three hydroxyls)
Examples
• CH3-CH(OH)-CH3
2-propanol
• CH3-CH(CH3)-CH2-CH2(OH)
3-methyl-1-butanol
• CH2(OH)-CH2-CH(OH)-CH3
1,3-butandiol
• Phenols are alcohols in which the –OH group
is attached to benzene.
• Name or give the formulas for the following:
a) CH3-CH(OH)-CH3
e) 2-pentanol
b) CH2(Cl)-CH(OH)-CH3
c) CH2(OH)-CH(OH)-CH2-CH3
d) C6H4(OH)(CH3)
f) 2,2,4-pentatriol
g) 3-ethyl-2-pentanol
h) 2-ethylphenol
Properties
• Alcohols tend to have high boiling points due to the
strong hydrogen bonding that occurs between these
molecules.
• Smaller molecules are also soluble in water as they
can hydrogen bond with the polar water molecules.
• Longer chain molecules tend to be insoluble as the
hydroxyl group has less effect on the molecule.
They can be good solvents for non-polar molecular
compounds (“like dissolves like”).
Ethers
• These are compound in which oxygen is
bonded between two carbon groups.
• The two-alkyl groups are named in
alphabetical order and followed by the word
“ether”.
CH3-CH2-CH2-O-CH3
CH3-CH2-O-CH2-CH3
methylpropyl ether
diethyl ether
Aldehydes and Ketones
• These two families share certain
structural features and chemical
properties.
• They both contain the carbonyl group
which we will show as (-C(=O)-) in our
condensed formulas.
• Aldehydes = chain + carbonyl group +
hydrogen
• Ketones = chain 1 + carbonyl group +
chain 2
Naming
• Aldehydes: change the “_e” ending to
“_al”
propanal
• Ketones: count the total number of
carbons present. Change the “_e”
ending to “_one”. Number the carbonyl
location.
propanone
3-hexanone
• Properties: - They have low boiling
points because they have no O – H
bonds for hydrogen bonding.
• -When added to water, though, they can
hydrogen bond to the water molecules
so they are quite soluble in water.
Try This
• Draw and name the aldehyde and the
ketone with the molecular formula of
C4H8O.
• AW p. 628, Name:
CH3CH2CHO
CH3-CH2- CH(CH3)-CH2-CHO
CH3-CH2-CH2-C(=O)-CH2-CH3
CH3-C(=O)-CH2-CH3
Carboxylic Acid
• These organic acids contain the
carboxyl functional group, -C(=O)-OH
which include both the carbonyl group
and the hydroxyl group. In molecular
formulas, the carboxyl group is often
presented as –COOH.
• Carboxylic acids create the sour taste in
foods and have distinctive odors.
• They are polar molecules and are both
hydrogen acceptors and hydrogen donors.
Thus they will readily form hydrogen bonds,
and smaller molecules are easily dissolved in
water.
• They have all of the properties of acids –
react with metals, make indicators change
color, etc.
Naming
•
Replace the “_e” ending with “_oic
acid”.
Propanoic acid
•
•
•
•
•
•
•
Name
a) CH3-CH2-CH2-C(=O)OH
b) CH3-C(CH3)(CH3)-C(=O)OH
c) COOH
Give the formula for
a) hexanoic acid
b) 3-methylpentanoic acid
Ester
• Esters are
derivatives of
carboxylic acids
in which the –
OH of the
carboxyl group
has been
replaced by an
– OR from an
alcohol.
Naming
•
•
•
The name of an ester has two parts:
Locate the alcohol branch and name it as
an alkyl group.
Locate the acid branch. The ending of the
acid name is changed from “_oic acid” to
“_oate”
ethyl propanoate
methyl ethanoate
Properties
• Esters are “odor” chemicals (fruits and
flowers).
• are added to foods to enhance taste +
odor.
Try This
• P. 411 McGraw Hill
a
b
c
Draw these
•
•
•
•
•
methyl pentanoate
heptyl methanoate
butyl ethanoate
propyl octanoate
ethyl 3,3-dimethylbutanoate
Amines and Amides
• There are two functional groups which
contain nitrogen atoms connected to
carbons: the amines and the amides.
amine
amide
• Amines and amides are abundant in
nature. They are a major component of
proteins and enzymes and nucleic
acids
• Many are toxic
• Amines with low molecular masses
smell like fish
• Many smells of decay are caused by
amines
Amines
• Amines are organic derivatives of
ammonia, NH3, in which one or more of
the three H’s is replaced by a carbon
group
• Amines are classified as primary (1°),
secondary (2°), or tertiary (3°),
depending on how many carbon
groups are connected to the nitrogen
atom.
Naming
• Identify the largest hydrocarbon group attached
to the N atom as the parent alkane.
• Replace the –e at the end with the new ending –
amine. Include a position number, if necessary,
to show the location of the functional group on
the hydrocarbon chain
• Name the other alkyl group(s) attached to the N
atom. Use the letter N- to locate the group(s). If
there are two, you will use N,N. This is the
prefix.
• Put together prefix + root + suffix
3 – hexanamine
There is a chain of
6 carbons and the
N group is located
at the third C.
N-ethyl-N-methyl-2-propanamine
The propyl group is the largest group. So
propane is the parent alkane.
The N atom is found off of the second C
A methyl group is attached to the N atom.
An ethyl group is attached to the N atom
Practice
• Name each amine:
a) CH3-NH2
b) CH3CH2CH(CH3)NH2
c)
d)
e)
f)
• Other examples:
• http://www.muhlenberg.edu/depts/chemistr
y/chem201woh/opa091203a.htm
Properties
• Tend to be polar
• Hydrogen bonding takes place
• Solubility decreases as the number of
carbon atoms increases
• Boiling points of primary and
secondary amines are higher than
boiling points of tertiary amines
Amides
• Has a carbon atom double-bonded to
an oxygen atom and single-bonded to
an nitrogen atom
Naming
•Locate the part of the amide that contains the C=O
group. Name the parent carboxylic acid from which
this part is derived. This is always position one.
•Replace the –oic acid with –amide
•Decisions:
•If there are two hydrogen atoms attached to the
N atom, there are no other prefixes
•If there is one alkyl group attached, name the
alkyl group and give it location letter N
•If there are two alkyl groups, place them in
alphabetical order. N must be used. If the groups
are identical, use N,N
•So: prefix + root + prefix
Examples
Methanamide
One alkyl group,
one carbon
One alkyl group,
two carbons
ethanamide
N-methylpropanamide
There are two alkyl
groups, a methyl and a
propyl
propyl
• 2-methylpropanoic
acid is the parent acid
• So the base name is
2-methylpropanamide
• A propyl group is
attached to the N
N-propyl-2-methylpropanamide
Properties
• N atoms attracts electrons more
strongly than C or H, so it is polar
• Hydrogen bonding (N-H)
• Soluble in water
• Many are solid at room temperature
•
•
•
•
•
Examples:
acetaminophen
Urea
Valium
Thalidomide