Download Organic Chemistry introduction

Organic Chemistry
Introduction
Alkanes
Nomenclature
Electron Dot structures
Li
Be
Class exercise 1:
Draw the electron
dot structure of
Carbon
B
C
N
O
F
Class exercise 2:
Draw the electron
dot structure of
oxygen and fluorine
Ne
Lewis Dot structures
Li
Be
B
C
N
O
F
Organic Chemistry


Chemistry of Carbon
Bonding of H,O, X and N
Valence Summary
C
H
O
N
Halogen
Valence
electrons
4
1
6
5
7
Valence
4
1
2
3
1
Single
Double
triple
single
Single
Double
Single
Double
triple
single
Bond types
Complete Structural Formulas
Show the bonds between each of the
atoms
H
H

H
CH
H
C

H
H
CH4 , methane
H
More Alkanes
H
H
H
H
C
C
H
H
Condensed Structural Formulas
H
CH3
CH3
Ethane
H
H
H
C
C
C
H
H
H
H
CH3 CH2 CH3
Propane
IUPAC Names
Name
# carbons
Structural Formula
Methane 1
CH4
Ethane
CH3CH3
2
Propane 3
CH3CH2CH3
Butane
CH3CH2CH2CH3
4
Pentane 5
CH3CH2CH2CH2CH3
IUPAC NAMES
Name
# carbons
Structural Formula
Hexane 6
CH3CH2CH2CH2CH2CH3
Heptane 7
CH3CH2CH2CH2CH2CH2CH3
Octane
8
CH3CH2CH2CH2CH2CH2CH2CH3
Nonane 9
CH3 CH2 CH2CH2CH2CH2CH2CH2CH3
Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
Learning Check Alk1
A. What is the condensed formula for
H H H H
H
C
C
C
C
H
H
H H
H
B. What is its molecular formula?
C. What is its name?
Solution Alk1
A.
CH3CH2CH2CH3
B.
C4H10
C.
butane
Properties of Alkanes
So what exactly do
these things do?
Physical Properties of Alkanes
1. Combustion - Alkanes are inflammable, i.e. they burn.
CH4
+
2 O2
CO2
+2 H2O
2. Boiling and melting points
a. Both bp and mp increase with increasing carbon number for
straight-chain
alkanes with formula CnH2n+2
Carbon Number
C1- C4
C5 – C16
C17 – C30
C30 – C50
>C50
Physical State
gases
liquids
oils and greases
paraffin waxes
plastics (polyethylene)
b. Branching tends to lower the boiling point and raise the melting point
BP
60oC
MP -154oC
58oC
50oC
-135oC
-98oC
Explanation:
MP Branching reduces the flexibility of the molecule which reduces the entropy term
S in the equation Tmp = H/S. Since S is in the denominator, Tmp increases.
BP Branching reduces surface area (more compact structure), and therefore London
dispersion forces which control boiling point for these molecules.
3. Solubility – alkanes are nonpolar molecules and therefore insoluble in water, which
is polar. Alkanes are hydrophobic.
4. Densities – alkanes are less dense than water, with densities near 0.7 g/mL. Therefore
they float on water, e.g. Exxon Valdez oil spill.
Naming Hydrocarbons
(nomenclature)
Drawing Structures: It’s All Good
H
C
2-butene
H
H
H
C
C
C
C
H
H
H
H
H3C
H
H3C CH CH CH3
CH
H3C
CH3
C
H
CH3
CH
CH3
H3C
This is called the
“condensed structure”
On a test, choose a
method that shows all Hs
CH3CH=CHCH3
Using brackets can also shorten some formulas:
CH3CH2CH2CH2CH2CH3 vs. CH3(CH2)4CH3
Basic Naming of Hydrocarbons
Hydrocarbon names are based on:
1)type,
2) # of carbons,
3) side chain type and position
1) name will end in -ane, -ene, or -yne
2) the number of carbons is given by a “prefix”
1 meth2 eth3 prop4 but5 pent6 hex7 hept8 oct9 non10 dec-
Basic Naming of Hydrocarbons
Q - What names would be given to these:
heptane, nonane
7C, 9C alkane
2C, 4C alkyne
ethyne, butyne
6C, 3C alkene
Hexene, propene
Mnemonic for First Four Prefixes
First four prefixes




MethEthPropBut-
Monkeys
Eat
Peeled
Bananas
Other Prefixes
Decade
?
Decimal
Decathalon

Pent-

Oct-

Dec-

Hex-, Hept-, Non-
Straight chain hydrocarbons
Learning Check

Pentane

Propane

Heptane

Ethane

Octane
Numbering Carbons
Q- draw pentene
A- Where’s the double H3C
5
1
bond? We # C atoms.
H
H
1-pentene
C
C
C
C
H
H
H
H
4
2
3
2
4
1
5
H
 Naming
compounds with multiple bonds is more
complex than previously indicated.
 When 2+ possibilities exist, #s are needed.
 Always give double bond the lowest number.
 Q - Name these
H
C
H
2
4
H3 C
C
2-butene
C
CH3
ethene
H3C
H
CH3 3-nonyne
Learning Check - Numbering Carbons

Name the following compounds:
2-butene
H3C
H3 C
C
H
H
C
C 2H 4
CH3
ethene
CH3 3-nonyne
CH3
Naming Side Chains
 The names of molecules
H3C
CH3
with branches are based
on: side chains, root
CH3
2,3-dimethylpentane
 The “root” or “parent chain” is usually the longest
possible hydrocarbon chain.
 The root must include multiple bonds if they are
present. If a cyclic structure is present it will be the
root even if it is not the longest chain.
 Side chains are also called “side branches” or
“alkyl groups”. Their names end in -yl.
Common side chains :
-CH3 methyl, -CH2CH3 ethyl, -CH2CH2CH3 propyl
IUPAC Rules for Naming Hydrocarbons
1.
2.
3.
4.
Choose the correct ending: -ane, -ene, or -yne
Determine the longest carbon chain. Where a double
or triple bond is present, choose the longest chain
that includes this bond. If there is a cyclic structure
present, the longest chain starts and stops within the
cyclic structure.
Assign numbers to each C of the parent chain. For
alkenes and alkynes the first carbon of the multiple
bond should have the smallest number. For alkanes
the first branch (or first point of difference) should
have the lowest #. Carbons in a multiple bond must
be numbered consecutively.
Attach a prefix that corresponds to the number of
carbons in the parent chain. Add cyclo- to the prefix
if it is a cyclic structure.
IUPAC Rules for Naming Hydrocarbons
5.
6.
7.
8.
Determine the correct name for each branch (“alkyl”
groups include methyl, ethyl, propyl, etc.)
Attach the name of the branches alphabetically, along
with their carbon position, to the front of the parent
chain name. Separate numbers from letters with
hyphens (e.g. 4-ethyl-2-methyldecane)
When two or more branches are identical, use
prefixes (di-, tri-, etc.) (e.g. 2,4-dimethylhexane).
Numbers are separated with commas. Prefixes are
ignored when determining alphabetical order. (e.g.
2,3,5-trimethyl-4-propylheptane)
When identical groups are on the same carbon,
repeat the number of this carbon in the name. (e.g.
2,2-dimethylhexane)
Naming Side Chains
Example: use the rules on this 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: determine the longest carbon chain
ene
Naming Side Chains
CH2
CH3 CH2 C
CH2 CH3
CH2 C
CH3
CH3
Rule 3: Assign numbers to each carbon
ene
Naming Side Chains
CH2
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
6
CH3
CH3
Rule 3: Assign numbers to each carbon
ene
Naming Side Chains
CH2
CH2 CH3
1
CH3 CH2 C
2
5
CH2 C
3
4
6
CH3
CH3
Rule 4: attach prefix (according to # of Cs)
1-hexene
ene
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
6
CH3
methyl
CH3
methyl
Rule 6: attach name of branches 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 7,8: 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 7,8: group similar branches
2-ethyl-4,4-dimethyl-1-hexene
Similar questions will be issued on Moodle and in the tutorial sheets
Learning Check – Naming
CH3 CH
CH2
propene
CH3 CH
CH3
CH CH3
CH3 CH CH C CH3
2,4-dimethyl-2-pentene
2-butene
CH
CH3
C
CH2 CH3
1-butyne
CH3
CH2 CH
C
CH3
CH2 CH3
CH3
CH3
C
CH
CH3
CH
CH2
CH2 CH3
c) 5-ethyl-4-methyl-2-heptyne
CH2
CH3
b) same
CH3
C
CH
CH2
a) 3,3-dimethyl-1-pentene
CH3
C