Download Organic Chem, Alkanes, Alkenes, Alkynes & Aromatics

Organic Chemistry
The study of carbon compounds.
Over 10 million compounds naturally exist
More than 300 000 are synthesized
Inorganic vs Organic
– oxides of carbon (CO2,
CO)
– carbonates,bicarbonates
(NaHCO3,CaCO3)
– cyanides (NaCN, etc)
– any carbon attached to a
metal and no H
• Hydrocarbons
containing CxHy
Origin of organic compounds
• Originally from “organic” meaning life
• Not just chemistry of life, chemistry of carbon
• Naturally occurring organic compounds are found in plants,
animals, and fossil fuels
• All of these rely on the “fixing” of C from CO2
• Synthetic organic compounds are derived from fossil fuels
or plant material
The diversity of carbon compounds is based on
the fact carbon atoms Form 4 Bonds
• Forms strong covalent and nonpolar bonds with itself
and other elements
Review:
• Lewis Structure, Structural formula, Line diagrams
Carbon molecules form complex 3-D shapes
Common Molecular Shapes
• Tetrahedral
• Trigonal planar
• Linear
• Angular
• Trigonal pyramidal
Simplest Hydrocarbons
Alkanes
C
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
H
Alkynes
C
Alkenes
C
H
H
C
H
H
H
C
C
C
C
C
H
H
H
H
H
Aromatics
C
H
H
C
C
C
H
H
H
C
C
C
H
H
H
H
H
H
H
C
C
C
C
H
C
C
H
H
Naming Hydrocarbons
(nomenclature)
Naming: common vs. IUPAC
• Common names used in the 1800’s are still used for some
compounds today: eg.
H
C
C
Commonly known
as Acetylene
H
IUPAC: Ethyne
• The International Union of Pure and Applied
Chemistry (IUPAC) was established in 1900s
• Systematic method allows an infinite number
of compounds to be named given a few rules
Mnemonic for first four prefixes
First four prefixes
•
•
•
•
MethEthPropBut-
Monkeys
Eat
Peeled
Bananas
Other prefixes
Decade
?
Decimal
• Pent• Oct-
• Dec-
Decathalon • Hex-, Hept-, Non-
Alkanes
• Are straight or branched-chain containing
only single bonds
• Are a homologous series –a group of
compounds whose members differ by the
addition of the same structural group
• Named by using prefix and ending -ane
TASK
• Write chemical and structural formula for all alkanes that
contain up to 10 carbons
•
•
•
•
•
•
•
•
•
•
•
Methane CH4
Ethane CH3CH3
Propane CH3CH2CH3
Butane CH3CH2CH2CH3
Pentane
Hexane
Heptane
Octane
Nonane
Decane
This is just the beginning……………………………………………………………..
You may have noticed that branching creates enormous variation
Try Naming These
CH2
H3C
CH2
CH2
CH2
CH2
CH2
CH2
CH3
CH2
Structural Isomers
• Substances with the same chemical formula
by different arrangements of atoms
• Eg.
Butane
& 2 methyl-propane
***Isomers have different physical and chemical properties
TASK: Draw all the isomers for
pentane and hexane
Did you know?
• 3 isomers of pentane
• 5 isomers of hexane
• Heptane-9
• Octane-18
• Nonane-35
• Decane-75
• making a total of 150 different possible alkane
compounds containing 10 carbons.
Greater complexity exists because organic compounds can
form Cyclic (ring) structures?
• Cyclic structures are circular
• Have “cyclo” in name
• Eg. Cyclopropane
Cyclopentane
H
CH2
H 2C
CH2
H
H
H
C
C
H
H
C
C
C
H
H
H
H
TASK
• Study the following graphic.
• What 2 trends can be
identified?
• Hypothesize why these trends
exist.
• TASK 2: Compare, contrast
and explain the physical
properties of the first 10 alkanes
Background: formulas for HxCy
• CH single bonds
Alkanes= CnH2n+2,
• CH with one double bond Alkenes= CnH2n,
• CH with two double bonds Alkynes= CnH2n-2
• Q - How many hydrogens in each of these:
Alkane C6H
Alkene C22H
H 3C
CH3
Basic names of hydrocarbons
• Hydrocarbon names are based on:
– 1) class
– 2) # of C,
– 3) side chain type
– 4) position
Q - What names would be given to these:
7C, 9C alkane heptane, nonane
2C, 4C alkyne ethyne, butyne
1C, 3C alkene
does not exist, propene
Numbering carbons
Q- draw pentene
A- Where’s the bond? H3C
5
1
We number C atoms
H
H
1-pentene
C
C
C
C
H
H
H
H
4
2
3
2
4
1
5
H
• Always start numbering for the carbon nearest the double
bond the lowest number
• Q - Name these
2-butene
H3C
H3 C
C
H
H
C
C 2H 4
CH3
Ethene
CH3 3-nonyne
Multiple multiple bonds
H 3C
CH3 2,3-heptadiene
H3C
C
C
C
C
C
C
2,4,6-nonatriyne
•
•
•
•
CH2
CH3
Rules
Give 1st bond lowest #
include di, tri, tetra, penta, etc. before ene/yne
Comma between #s, hyphen between #-letter
H
H
C
H
C
C
C
HC
2-butyne
H
H2C
C
CH2
CH
1,2,4-pentatriene
CH3CH2CH2CH=C=CH2 1,2-hexadiene
H
H
Cyclic structures
Q- Draw these:
cyclobutene
1,3-cyclopentadiene
H
H2C
CH2
HC
CH
H
H
C
C
C
H
cyclopropane
C
C
H
CH2
H
H 2C
CH2
Naming side chains
CH3
H3C
• Names are made up
of: side chains, root
• 2,3-dimethylpentane
CH3
• Root is the longest possible HC chain
• Must contain multiple bonds if present
• Add -yl to get name of side chain H C
3
• Common side chains include:
CH3- methyl
CH3CH2- ethyl
CH3CH2CH2- propyl (CH3)2CHisopropyl
CH3
CH
*
CH3
Naming side chains
Example: use the rules on the bottom of
handout to name the following structure
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 1: choose the correct ending
ene
Naming side chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 2: longest carbon chain
ene
Naming side chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 3: attach prefix (according to # of C)
1-hexene
ene
Naming side chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 4: Assign numbers to each carbon
1-hexene
Naming side chains
CH2
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
6
CH3
CH3
Rule 4: Assign numbers to each carbon
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 5: Determine name for side chains
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 6: attach name of branches
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 7: list alphabetically
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 8,9: group similar branches
2-ethyl-4-methyl-4-methyl-1-hexene
1-hexene
Naming side chains
CH2
ethyl
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
CH3
6
CH3
methyl
methyl
Rule 8,9: group similar branches
2-ethyl-4,4-dimethyl-1-hexene
Try Naming Side Chains
H3C
H3C
CH2
CH CH3
H2C
CH2
CH CH CH2 CH3
H3C
CH3
3-methylhexane
CH2 CH2 CH3
CH
CH3
4-ethyl-2,3-dimethylheptane
CH3
CH3
CH3
CH3 CH2 CH CH CH CH2 CH CH3
CH2 CH3
5-ethyl-2,4,6-trimethyloctane
Naming side chains
Name the structures below
CH3
CH
H3C
CH2
CH
CH3
H2C
H3C
H3C
3-ethyl-2-methylpentane
CH3
CH3
3-ethyl-1,5,5trimethylcyclohexene
CH3
Try Drawing These
2,2-dimethyloctane
1,3-dimethylcyclopentane
1,1-diethylcyclohexane
6-ethyl-5-isopropyl-7-methyl-1-octene
Try Naming
CH3 CH3
H3C
CH3
CH3 CH3
Aromatic Hydrocarbons
• Aromatic compounds contain benzene ring
structures and their derivatives.
• Benzene (C6H6)
• most commonly used organic (nonpolar)
solvent
• very stable substance, unreactive
• toxic if inhaled-carcinogenic
• produced by processing coal, crude oil,
gasoline or the combustion of rubber tires
• if it occurs as a side chain it is called a
phenyl group
Resonance
• The properties of this compound can be explained by following theory:
-the chemical bonds between carbon atoms are not single or double
-all bonds between carbons in the benzene ring are identical in length and
strength
-there is an even distribution of valence electrons around the entire molecule.
• The resonance of the single and double bonds accounts for the stability of
aromatic compounds.
• This is illustrated by resonance structures:
Aromatic nomenclature
H3C
There are 2 naming methods
H3C
1) Numbering carbons
2) ortho, meta, para (stomp) 1,2-dimethylbenzene
orthodimethylbenzene
CH3
ST Ortho
Meta
H3C
H3C
Para
1,3-dimethylbenzene
metadimethylbenzene
H3C
CH3
1,4-dimethylbenzene
paradimethylbenzene