Transcript Chapter 17: Organic Chemistry

Chapter 17:
Organic Chemistry
Chem 1110
Figures: Basic Chemistry 3rd Ed., Timberlake and Timberlake
Organic Chemistry
Organic Chemistry is the chemistry of carbon
containing molecules
• Originally thought to be produced only by
living things… organic
Chemistry is the study of the composition,
structure and reactions of matter
• The Structure of molecules is very important
in organic and biochemistry
IUPAC Names:
Organic Molecule Prefixes
Structural Formulas Revisited
Alkanes are written as structural formulas:
• Revisit Chapter 6 for more details
• Expanded Structure shows each bond
• Condensed Structures show each carbon atom
and the attached hydrogen atoms
Drawing Structural (Line) Formulas
Carbon atoms in a chain:
• maintain their tetrahedral shape
• are connected in a zigzag pattern
• are drawn as two dimensional
• can be written in many ways
• have free rotation in straight chain
Conformers
• Remember, organic compounds have free rotation
around sp3 carbon atoms, this leads to a variety of
spatial orientations for the same structure
• Conformers: different orientations of the same
molecule:
Conformers
Let’s consider different conformers of pentane, C5H12:
Isomers
Isomers:
• Compounds with the
same molecular
formula but different
atomic arrangements
For Example:
• Butane (C4H10) has a
straight chain and a
branched chain form
Isomers
Let’s consider different isomers of pentane, C5H12:
Alkanes with Substituents
In the IUPAC system:
• a carbon branch is named an alkyl-group
• halogen atoms are named as halo-group
Naming Alkanes
1. Find longest alkane chain
2. Name and number substituents
3. Substituents are numbers to give the lowest
number possible
4. Substituents are named in alphabetical order,
ignore prefixes di-, tri-, etc…
Naming Alkanes
Learning Check
Provide the IUPAC name for the following:
Cl
CH3
|
|
CH3─CH2─CH─CH2─C─CH2─CH3
|
Cl
Drawing Alkanes from Names
2,2,3-trimethylpentane
2,4-dibromo-3-ethylhexane
Take Home
Draw the condensed and line structure for
2-bromo-4-chlorobutane.
Classifying Carbon Atoms
Primary (1°): attached to one other carbon
Secondary (2°): attached to two other carbons
Tertiary (3°): attached to three other carbons
Quaternary (4°): attached to four other carbons
Cycloalkanes
Saturated compounds with a ring structure
• Have a loss of free rotation
• Formed by removal of a H atom form each
end carbon
Butane, C4H10
Cyclobutane, C4H8
Cycloalkanes
Saturated compounds with a ring structure
that have a loss of free rotation
• Practice drawing cyclohexane, C6H12
Unsaturated Hydrocarbons
Alkenes contain a carbon-carbon double
bond (C = C)
• Have a fixed structure around the C=C
• Named for the longest carbon chain which
includes the base alkene
Alkynes contain a carbon-carbon triple
bond (C ≡ C)
• Named for the longest carbon chain which
includes the base alkyne
Alkenes and Alkynes
cis and trans Isomers of Alkenes
Alkenes have two different isomers that are determined
by what groups lie on each side of the double bond:
• cis: substituent groups are on the same side of the
double bond
• trans: substituent groups are on the opposite side
of the double bond
• MUST have two different groups on C
cis and trans Isomers
Alkynes
NO rotation around the C≡C and have a straight
line structure at the triple bond:
•
EXAMPLE:
Reactions of Alkenes
Addition Reactions (Combination Reactions):
•
Reactants add across the double bond
•
H2 (hydrogenation) and halogens (F2, Br2, Cl2)
+ 3 H2
Reactions of Alkenes
Addition Reactions (combination reactions)
•
HF, HCl, HBr, HI
+ HCl
•
H2O, creates an alcohol
+ H2O
Polymerization of Alkenes
Polymerization is an Addition Reaction:
•
Addition reaction where one alkene
combines with another alkene
•
Polymer: A molecule with a high molar
mass made up of thousands of
repeating units.
Monomer: individual molecules used to
produce the polymer.
•
Synthetic Polymers in Everyday
Items
Polymerization
In polymerization, small repeating units called
monomers join to form a long-chain polymer
Learning Check
What is the structure of polypropylene?
Take Home
What is the structure of polystyrene
(polyphenylethene)?
Recycling Plastics
Recycling is simplified by using codes found on
plastic items:
Reactions of Alkynes
•
Alkynes react very similarly to alkenes
but often can add two moles of reactant
per mole of alkyne (due to triple bond)
Aromatic Compounds
Benzene (C6H6):
• has six electrons shared equally among six carbon
atoms in a ring
• is written as two possible ring structures
• is also represented as a hexagon with a circle
drawn inside (common line structure shorthand)
Common Aromatic Compounds
in Nature and Health
Learning Check
Select the correct name for the following structure:
1) chlorohexane
2) chlorobenzene
3) 1-chlorobenzene
Learning Check
Write the IUPAC name of the following compound:
CH3
Cl
Take Home
Draw the condensed structural formula for
1-bromo-3,4-dichlorobenzene.
Alcohols and Ethers
• An alcohol contains the
hydroxyl (-OH)
functional group
• In an ether, an oxygen
atom is bonded to two
carbon atoms
Aldehydes and Ketones
Contain a carbonyl group (C=O)
• In an aldehyde, the carbonyl
group is attached to another carbon
atom and one hydrogen atom
• In a ketone, the carbonyl group
attached to two other carbon atoms
Oxidation Reactions
In organic chemistry (and biochemistry):
• Oxidation Reactions typically involve the addition
of bonds to oxygen
• Reduction Reactions typically involves a gain of
hydrogen
Classification of Alcohols
Alcohols are:
• classified by the number of carbon groups attached
to the carbon atom bound to the -OH group:
 Primary Alcohol when one carbon group attached
 Secondary Alcohols when two carbon groups are
attached
 Tertiary Alcohols when three carbon groups are
attached
Classification of Alcohols
Alcohols are:
• classified by the number of carbon groups attached
to the carbon atom bound to the -OH group:
Learning Check
Classify the following as 1°, 2°, or 3° alcohols:
A. CH3─CH2─CH2─OH
C.
OH
│
CH3─C─CH2─CH3
│
CH3
OH
│
B. CH3─CH─CH2─CH3
Oxidation of 1 Alcohols form Aldehydes
In the oxidation [O] of a primary alcohol (1):
• one H is removed from the –OH group
• another H is removed from the C bonded to the –OH
primary alcohol
aldehyde
OH
│
CH3─C─H
│
H
O
║
CH3─C─H + HOH
Ethanol
(ethyl alcohol)
Ethanal
(acetaldehyde)
Oxidation of 2 Alcohols
The oxidation of 2 alcohols is similar, but a
ketone is formed:
secondary alcohol
ketone
OH
│
CH3─C─CH3
│
H
O
║
CH3─C─CH3 + HOH
2-propanol
(isopropanol)
2-propanone
(acetone)
Oxidation of 3 Alcohols
Tertiary (3) alcohols do not readily oxidize:
Tertiary alcohol
OH
│
CH3─C─CH3
│
CH3
no product
NO H on the C─OH to oxidize
2-Methyl-2-propanol
Oxidation of Ethanol in the Body
In the body:
• Enzymes (proteins) in the liver oxidize ethanol
• the aldehyde product impairs coordination
• blood alcohol over 0.4% can be fatal
CH3CH2OH
Ethanol
O
║
CH3CH
Acetaldehyde
O
║
CH3COH
Acetic acid
2 CO2 + H2O
Percent Blood Alcohol
Concentration
A breathalyzer test is
used to determine
blood level of ethanol
Carboxylic Acids and Esters
Both contain a carboxyl group,
a carbonyl group attached to a
hydroxyl group
• A carboxylic acid contains a
terminal carboxyl group
• An ester contains the carboxyl
group between carbon atoms
• The H on the hydroxyl is
replaced by the C-C bond
Amines and Amides
Contain a nitrogen atom or
nitrogen containing group
• In an amine, the functional
group is a nitrogen atom
• In amides, the hydroxyl group
of a carboxylic acid is replaced
by a nitrogen group