Upload
phamcong
View
237
Download
5
Embed Size (px)
Citation preview
2
Organic Chemistry and Biochemistry
The study of carbon-containing
compounds and their properties.
The vast majority of organic
compounds contain chains or rings
of carbon atoms.
The study of the chemistry of living
matter
3
Hydrocarbons
compounds composed of carbon and
hydrogen.
Saturated compounds (alkanes) have
the maximum number of hydrogen
atoms attached to each carbon atom
H C
H
H
C
H
H
H
4
Unsaturated compounds have fewer
hydrogen atoms attached to the carbon
chain than alkanes
Unsaturated: They contain carbon-carbon
multiple bonds (double or triple)
H C
H
H
C
H
C
H
H
5
22.1 Alkanes: Saturated hydrocarbons
Saturated hydrocarbons, CnH2n+2
“Saturated” because they can’t take
any more hydrogen atoms
Normal straight chains (unbranched
hydrocarbons)
H3C–(CH2)n–2–CH3
Waxes, oils, & fuel gases as n
decreases.
10
The First 10 “Normal” Alkanes
Name Formula M.P. B.P. # Structural Isomers
Methane CH4 -183 -162 1
Ethane C2H6 -172 -89 1
Propane C3H8 -187 -42 1
Butane C4H10 -138 0 2
Pentane C5H12 -130 36 3
Hexane C6H14 -95 68 5
Heptane C7H16 -91 98 9
Octane C8H18 -57 126 18
Nonane C9H20 -54 151 35
Decane C10H22 -30 174 75
C1 - C4 are Gases
at Room Temperature
C5 - C16 are Liquids
at Room Temperature
11
IUPAC Rules for Naming Branched Alkanes
• Find and name the parent chain in the hydrocarbon -
this forms the root of the hydrocarbon name
• Number the carbon atoms in the parent chain
starting at the end closest to the branching
• Name alkane branches by dropping the “ane” from
the names and adding “yl”. A one-carbon branch is
called “methyl”, a two-carbon branch is “ethyl”,
etc…
• When there are more than one type of branch (ethyl
and methyl, for example), they are named
alphabetically
• Finally, use prefixes to indicate multiple branches
12
Rules for Naming Alkanes
1. For alkanes beyond butane, add -ane to
the Greek root for the number of
carbons.
C-C-C-C-C-C : hexane
2. Alkyl substituents: drop the -ane and
add -yl
-C2H5 is ethyl
14
Rules for Naming Alkanes
3. Positions of substituent groups are specified by numbering the longest chain sequentially.
C C-C-C-C-C-C
3-methylhexane
Start numbering at the end closest to the branching
4. Location and name are followed by root alkane name. Substituents are given in alphabetical order and use di-, tri-, etc.
15
Normal vs Branched Alkanes
Normal alkanes consist of
continuous chains of
carbon atoms
Alkanes that are NOT
continuous chains of
carbon atoms contain
branches
The longest continuous
chain of carbons is called
the parent chain
CH3
CH2
CH2
CH2
CH3
CH3
CH2
CH
CH3
CH3
16
Structural Isomerism
Structural isomers are
molecules with the same
chemical formulas but
different molecular
structures - different
“connectivity”.
They arise because of the
many ways to create
branched hydrocarbons.
CH3
CH2
CH2
CH2
CH3
CH3
CH2
CH
CH3
CH3
n-pentane, C5H12
2-methlbutane, C5H12
17
Example : Show the structural formula
of 2,2-dimethylpentane
The parent chain is indicated by the ROOT of the name - “pentane”. This means there are 5 carbons in the parent chain.
CH3
CH2
CH2
CH2
CH3
• “dimethyl” tells us that there are
TWO methyl branches on the
parent chain. A methyl branch is
made of a single carbon atom.
• “2,2-” tell us that BOTH methyl
branches are on the second
carbon atom in the parent chain.
CH3
1
C
CH23
CH2
4
CH35
CH3
CH3
1
2
3
4
5
18
Example: Structural formula of 3-ethyl-2,4-dimethylheptane?
The parent chain is
indicated by the ROOT
of the name -
“heptane”. This means
there are 7 carbons in
the parent chain.
CH3
CH2
CH2
CH2
CH2
CH2
CH3
• “2,4-dimethyl” tells us there are
TWO methyl branches on the
parent chain, at carbons #2 and
#4.
• “3-ethyl-” tell us there is an ethyl
branch (2-carbon branch) on
carbon #3 of the parent chain.
1
2
3
4
5
7 6
CH3
CH
CH
CH
CH2
CH2
CH3
CH2
CH3
CH3
CH3
19
Example: 2,3,3-trimethyl-4-propyloctane
The parent chain is indicated
by the ROOT of the name -
“octane”. This means there
are 8 carbons in the parent
chain.
• “2,3,3-trimethyl” tells us there are
THREE methyl branches - one on
carbon #2 and two on carbon #3.
• “4-propyl-” tell us there is a propyl
branch (3-carbon branch) on
carbon #4 of the parent chain.
1
2
3
4
5
7
6
8
1
2 3
4
5
7
6
8
CH
C
CH
CH2
CH2
CH2
CH3
CH3
CH3
CH3
CH3
CH2
CH2
CH3
20
Example : Name the molecules shown
parent chain has 5 carbons -
“pentane”
two methyl branches - start
counting from the right - #2
and #3
2,3-dimethylpentane
CH3
CH2
CH
CH
CH3
CH3
CH3
parent chain has 8 carbons - “octane”
two methyl branches - start counting
from the left - #3 and #4
one ethyl branch - #5
name branches alphabetically
3,4-dimethyl
4 3
octane
5
5-ethyl-
21
Reactions of alkanes
Combustion reactions
2C4H10 + 13 O2 8CO2 + 10 H2O(g)
Substitution Reactions
CH4 + Cl2 CH3Cl + HCl
CH3Cl + Cl2 CH2Cl2 + HCl
CH2Cl2 + Cl2 CH Cl3 + HCl
CHCl3 + Cl2 C Cl4
23
Cyclic alkanes
CnH2n
A cycloalkane is made of a hydrocarbon
chain that has been joined to make a
“ring”.
CH
3
CH2
CH3 CH
2
C
H2
CH2
n-propaneC3H8
cyclopropaneC3H6
60° bond angleunstable!!
109.5° bond angle
•Note that two hydrogen atoms were lost in forming the ring
25
Cyclohexane - Boat & Chair Conformations
Cyclohexane is NOT a planar molecule. To achieve
its 109.5° bond angles and reduce angle strain, it
adopts several different conformations.
The BOAT and CHAIR (99%) are two conformations
Boat
chair
26
22.2 Alkenes and Alkynes
Alkenes: hydrocarbons that contain a
carbon-carbon double bond. [CnH2n]
C=C Ethene
CC=C propene
Alkynes: hydrocarbons containing a
carbon-carbon triple bond. [CnH2n-2]
C ΞC Ethyne
CCC Ξ CC 2-pentyne
27
Alkenes & Alkynes
Alkenes are
hydrocarbons that
contain at least one
carbon-carbon double
bond
Alkynes are
hydrocarbons that
contain at least one
carbon-carbon triple
bond
The suffix for the parent
alkane chains are
changed from “ane” to
“ene” and “yne”
e.g. ethene, ethyne
Where it is ambiguous,
the BONDS are
numbered like branches
so that the location of the
multiple bond may be
indicated
28
n2Hnnes, CeAlk
Cycle formation isn’t the only possible
result of dehydrogenation.
Adjacent C’s can double bond, C=C,
making an (unsaturated) alkene.
Sp2
29
Nomenclature for Alkenes
1. Parent hydrocarbon name ends in -ene
C2H4; CH2=CH2 is ethene
2. With more than 3 carbons, double bond
is indicated by the lowest numbered
carbon atom in the bond.
C=C-C-C is 1-butene
31
Cis and Trans Isomers
Double bond is fixed (rotation around the
double bond is restricted)
Cis/trans Isomers are possible
CH3 CH3 CH3
CH = CH CH = CH
cis trans CH3
32
Reactions of alkenes and alkynes
in which (weaker) bonds are broken
and new (stronger) bonds are formed
to atoms being added.
1. Addition Reactions
33
Hydrogenation reaction
Adds a hydrogen atom to each carbon atom
of a double bond H H H H catalyst
H–C=C–H + H2 H–C–C–H H H Ethene Ethane
CH3-CH3
34
Halogenation reaction
Adds a halogen atom to each carbon atom of
a double bond H H H H catalyst
H–C=C–H + Cl2 H–C–C–H Cl Cl Ethene Dichloro ethane
36
Alkynes, CnH2n–2
Carbon-carbon triple bonds
Names end in -yne
HCCH ethyne(acetylene)
HCC-CH3 propyne
•sp triple bonding makes a rigid 180°
segment in a hydrocarbon.
38
Naming Alkenes and Alkynes
When the carbon chain has 4 or more C atoms,
number the chain to give the lowest number to the
double or triple bond.
1 2 3 4
CH2=CHCH2CH3 1-butene
CH3CH=CHCH3 2-butene
CH3CHCHCH3 2-butyne
39
Question
Write the IUPAC name for each of the following
unsaturated compounds:
A. CH3CH2CCCH3
CH3
B. CH3C=CHCH3 C.
CH32-pentyne
2-methyl-2-butene 3-methylcyclopentene
40
Question
Name the following compound
CH3CH2C CCHCH2CH3
CH2
CH3
CH3CH2C CCHCH2CH3
CH2
CH3
1 2 3 4 5 6 7
5-ethyl-3-heptyne
41
Additions reactions:Hydrogenation and
Halogenation
Hydrogens and halogens also add to
the triple bond of an alkyne.
CH3C CCH2CH3 + Br2 CH3C CCH2CH3
Br Br
Br Br
42
22.3 Aromatic hydrocarbons
Unsaturated Cyclic hydrocarbons
Alternating single/double bond
cycles occur in many organic molecules
This class is called “aromatic” (by
virtue of their aroma).
• Delocalized bonds
possess a great stability
thus benzene does not
react like unsaturated
hydrocarbons
43
Benzene C6H6
sp2
sp2 sp2
The structure is
often preserved in
benzene chemical
reactions
Aromatic rings
do not add, they
substitute instead
44
Shorthand notation for benzene rings
The bonding in the
benzene ring is a
combination of different
Lewis structures
45
Aromatic Hydrocarbons
Substitution reaction
+ Cl2
FeCl3
Cl
+ HCl
+H2O
+HCl
benzene
Chlorobenzene
H
N
O
3
HNO3
CH3Cl
-NO2
-CH3
Nitroobenzene
Toluene
49
22.4 Hydrocarbon Derivatives
(Functional Groups)
Molecules that are fundamentally hydrocarbons
but have additional atoms or group of atoms
called functional groups
Part of an organic molecule where chemical
reactions take place
Replace an H in the corresponding alkane
Provide a way to classify organic compounds
50
The Common Functional Groups
Class General Formula
Halohydrocarbons RX
Alcohols ROH
Ethers ROR
Aldehydes R C
O
H
52
Some Types of Functional Groups
Haloalkane -F, -Cl, -Br CH3Cl
Alcohol -OH CH3OH
Ether -O- CH3-O-CH3
Aldehyde
Ketone
C H
O
CH3CH
O
C
O
CH3CCH3
O
53
More Functional Groups
Carboxylic acid -COOH CH3COOH
Ester -COO- CH3COOCH3
Amine -NH2 CH3NH2
Amide -CONH2 CH3CONH2
55
Haloahydrocarbons
An alkane in which one or more H atoms is
replaced with a halogen (F, Cl, Br, or I)
CH3Br bromomethane
Br (methyl bromide)
CH3CH2CHCH3 2-bromobutane
Cl
chlorocyclobutane
57
Substituents
List other attached atoms or groups in
alphabetical order
Br = bromo, Cl = chloro
Cl Br
CH3CHCH2CHCH2CH2CH3
4-bromo-2-chloroheptane
1 2 3 4 5
59
Alcohols: R–OH The –OH makes alcohol polar enough to
hydrogen bonding
Thus, they are water soluble
Ethanol is produced by the fermentation of
glucose
yeast C6H12O6
Glucose 2CH3CH2OH
Ethanol + 2 CO2
CO + 2H2O CH3OH
Methanol
• Methanol is produced industrially by hydrogenation
of carbon monoxide
60
Uses of alcohols
Methanol is used to synthesize adhesives, fibers,
plastics and recently as motor fuel
It is toxic to human and can lead to blindness and
death
Ethanol can be added to gasoline to form gasohol
and used in industry as solvent
Commercial production of ethanol:
CH2=CH2 + H2O CH3CH2OH
61
Classes of alcohols
R CH2OH
Primary alchol
CHOHR'
RSecondary alcohol
CR'R
R"OH
Tertiary alcohol
Alcohols can be classified according to the
number of hydrocarbon fragments bonded to
the carbon where the –OH group is attached
62
Naming Alcohols
In IUPAC name, the -e in alkane name is
replaced with -ol.
CH4 methane
CH3OH methanol (methyl alcohol)
CH3CH3 ethane
CH3CH2OH ethanol (ethyl alcohol)
64
Some Typical Alcohols
OH
“Rubbing alcohol” CH3CHCH3
2-propanol (isopropyl alcohol)
Antifreeze HO-CH2-CH2-OH
1,2-ethanediol (ethylene glycol)
65
Naming Alcohols
IUPAC names for longer chains number the chain from the end nearest the -OH group.
CH3CH2CH2OH 1-propanol
OH
CH3CHCH3 2-propanol
CH3 OH
CH3CHCH2CH2CHCH3 5-methyl-2-hexanol
5 2
67
Aldehydes and Ketones
In an aldehyde, an H atom is attached to a carbonyl
group
O carbonyl group
CH3-C-H
In a ketone, two carbon groups are attached to a
carbonyl group
O carbonyl group
CH3-C-CH3
68
Naming Aldehydes
IUPAC name: Replace the -e in the alkane name by -al
Common Add aldehyde to the prefixes form (1C), acet (2C), propion(3), and butry(4C)
O O O H-C-H CH3-C-H CH3CH2C-H
methanal ethanal propanal
(formaldehyde) (acetaldehyde) (propionaldehyde)
methane ethane propane
69
Aldehydes as Flavorings
CH
O
CH
O
HO
OCH3
CH=CH CH
O
Benzaldehyde Vanillin Cinnamaldehyde(almonds) (vanilla beans) (cinnamon)
70
Naming Ketones
IUPAC name: the -e in the alkane name is replaced with –one
and a number to indicate the position of carbonyl group when
needed.
In the common name, add the word ketone
after naming the alkyl groups attached to the
carbonyl group
O O
CH3 -C-CH3 CH3-C-CH2-CH3
2-Propanone 2-Butanone
(Dimethyl ketone) (Ethyl methyl ketone)
O
Cyclohexanone
Acetone
propane
butane
cyclohexane
71
Name the following compounds
O
A. CH3CH2CCH3 B.
2-butanone (ethyl methyl ketone)
CH3 O
C. CH3-C-CH2CH cyclohexanone CH3
3,3-dimethylbutanal
O
72
Draw the structural formulas for each of the following
compounds
CH3 O
A. 3-Methylpentanal CH3CH2CHCH2CH
Br O
B. 2,3-Dibromopropanal Br-CH2CHCH
O
C. 3-Methyl-2-butanone CH3CHCCH3
CH3
73
Preparation of aldehydes and Ketones
They are produced by oxidation of alcohols:
CH3CH2OH Oxidation
CH3CHCH3
OH
Oxidation CH3CCH3
O
CH3C
O
Hacetaldehyde
acetone
Primary alcohol
Secondary alcohol
ethanal
propanone
74
Carboxylic Acids and Esters
Carboxylic acids contain the carboxyl group as
carbon 1.
O
R
CH3 — C—OH CH3—COOH
carboxyl group
General formula R—COOH
75
Nomenclature of Carboxylic Acids
Formula IUPAC Common
alkan -oic acid prefix – ic acid
HCOOH methanoic acid formic acid
CH3COOH ethanoic acid acetic acid
CH3CH2COOH propanoic acid propionic acid
CH3CH2CH2COOH butanoic acid butyric acid
76
IUPAC nomenclature for Carboxylic acids
Identify longest chain
Number carboxyl carbon as 1
CH3
|
CH3 — CH—CH2 —COOH
3-methylbutanoic acid
1 2 3 4
78
Reaction of carboxylic acid with alcohol
CH3CO
OH + H OCH2CH3
CH3C
O
OCH2CH3 + H2O
Ester
Carboxylic acid Alcohol
Esterification
79
Esters
In ester, the H in the carboxyl group is replaced with
an alkyl group
O
CH3 — C—O —CH3 CH3—COO —CH3
ester group
•Esters give fruity odors
80
Naming Esters
• The parent alcohol is named first with a –yl ending
• Change the –oic ending of the parent acid to –ate
acid alcohol
O
methyl
CH3 — C—O —CH3
Ethanoate methyl ethanoate (IUPAC)
(acetate) methyl acetate (common)
81
Amines
Organic compounds of nitrogen N; derivatives of ammonia
Classified as primary, secondary, tertiary
CH3 CH3
CH3—NH2 CH3—NH CH3—N — CH3
Primary Secondary Tertiary
one N-C two N-C three N-C
bond bonds bonds
82
Naming Amines
IUPAC aminoalkane Common alkylamine
CH3CH2NH2
aminoethane
(ethylamine)
NH2
|
CH3CHCH3
2-aminopropane Aniline
(isopropylamine)
NH2
83
22.5 Polymers
Poly= many; mers=parts
Polymers are large, usually chainlike
molecules that are built from small
molecules called monomers joined by
covalent bonds
Monomer Polymer
Ethylene Polyethylene
Vinyl chloride Polyvinyl
chloride
Tetrafluoroethylene Teflon
85
Types of Polymerization
Addition Polymerization: monomers “add
together” to form the polymer, with no other
products. ( Polyethylene and Teflon)
Condensation Polymerization: A small
molecule, such as water, is formed for each
extension of the polymer chain. (Nylon)
86
Addition Polymerization
OH
C CH
H
H
HC
OH
H C
H
H
H
C CH
H
H
H
C
OH
H C
H
H
H
C
OH
H C
H
H
H
C CH H
H H
The polymerization process
Is initiated by a free radical
A species with
an unpaired
electron such as
hydroxyl free radical
Free radical attacks and break
The bond of ethylene molecule
To form a new free radical
• Repetition of the process thousands of times creates a long chain
polymer
• The process is terminated when two radicals react to form a bond;
thus there will be no free radical is available for further repetitions.
87
Condensation Polymerization
Formation of Nylon
N
H
H(CH2)6 N
H
H CO
O(CH2)4H
CO
O H
Hexamethylendiamine Adipic acid
N
H
H(CH2)6 N
H
C (CH2)4 CO
O H
O
+ H2O
• Small molecule such as H2O is formed
from each extension of the polymer chain
• both ends are free to react
Dimer
Diamine Dicarboxylic acid