Transcript Introduction to Organic Chemistry

Organic Chemistry
Nomenclature:
Alkanes
What is Organic
Chemistry?
Study of hydrocarbons and derivatives
7 million Organic Compounds
1.5 million Inorganic Compounds
Animal and plant matter, Foods,
Pharmaceuticals, Cosmetics, Fertilizers,
Plastics, Petrochemicals, Clothing
Organic Compounds
 Contain
carbon
 Have
covalent bonds
 Have
low melting points
 Have
low boiling points
 Burn
in air (oxygen)
 Are
soluble in nonpolar solvents
 Form
large molecules
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Crude oil can have different components
depending on where in the world it comes from
Where is the oil going?
US
Middle East
Petroleum Reserves (%)
7
65
World Population (%)
5
3
World Petroleum
Consumption (%)
31
6
How is Crude Oil Refined?
Distillation towers
Separated by the
physical property
of …
Boiling Point
Boiling Point Trends
Small molecules
low boiling points
usually gases at room temperature
Large molecules
high boiling points
usually liquids and solids at room
temperature
Sources of Organic Compounds
Fractional Distillation of Crude Oil
Barrel of crude oil
42 Gallons
Priced by the Barrel
$101 today
1 year ago: $90
Alkanes
• Hydrocarbon chains where all the bonds
between carbons are SINGLE bonds
• sp3 Hybridized Orbitals– tetrahedral,109.5o
• Name uses the ending –ane
• Examples: Methane, Propane, Butane,
Octane, 2-methylpentane
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
Prefixes for # of Carbons
1
Meth
6
Hex
2
Eth
7
Hept
3
Prop
8
Oct
4
But
9
Non
5
Pent
10
Dec
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
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?
What is the
General formula
for Alkanes?
Summary: IUPAC Rules for Alkane
Nomenclature
1. Find and name the longest continuous carbon
chain.
AKA: parent chain.
2. Number the chain consecutively, starting at the end
nearest an attached group (substituent).
3. Identify and name groups attached to this chain.
(Examples: methyl-, bromo-, etc.)
4. Designate the location of each substituent group
with the number of the carbon parent chain on which
the group is attached. Place a dash between
numbers and letters. (Example: 3-chloropentane)
5. Assemble the name, listing groups in alphabetical
order.
The prefixes di, tri, tetra etc., used to designate
several groups of the same kind, are not considered
when alphabetizing. Place a comma between multiple
numbers. (Example: 2,3-dichloropropane)
Step 1. Find the parent chain.
• Where is the longest continuous chain of
carbons?
Endings
• Alkanes (all C-C single bonded parent
chain) end in –ane
– Methane CH4
– Ethane C2H6
– Propane C3H8
• Attached carbon groups (substituents) end
in –yl
– Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –
3-ethylpentane
Step 2. Number the parent chain.
• Number the parent chain so that the
attached groups are on the lowest
numbers
Methyl is on carbon #2 of the parent chain
Methyl is on carbon #4 of the parent chain
1
5
1 8
2
4
3
3
4
2
3 6
7 2
8 1
4 5 5 4
6 3
5
1
GREEN is the right
way for this one!
27
1
7
2
6
3
5
4
4
Groups on 2 and 5
Groups on 4, 6, and 7
Groups on 2, 3, and 5
5
3
6
72
1
Groups on 3 and 6
Step 3. Name the attached groups.
• Carbon (alkyl) groups
– Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –
• Halogens
– Fluoro (F-)
– Chloro (Cl-)
– Bromo (Br-)
– Iodo (I-)
Step 4. Designate where the group
is attached to the parent chain.
• Use the numbers of the parent chain from
step 2 to designate the location of the
attached groups to the parent chain.
2-methyl
1
2
3
4
5
Step 5. Alphabetize the groups,
combine like groups, and assemble.
• The prefixes di, tri, tetra
etc., used to designate
several groups of the
same kind
• Prefixes are not
considered when
alphabetizing (Example:
dimethyl = m for
alphabetizing)
• Parent chain goes LAST
1,1,1-trichloro-1fluoromethane
1,1-dichloro-1,1difluoromethane
Draw Some Simple Alkanes
• 2-methylpentane
• 3-ethylhexane
• 2,2-dimethylbutane
• 2,3-dimethylbutane
Structural Formulas
• “Lazy” way to write the Hydrogens
• Instead of drawing the bonds, just state
how many hydrogens are attached
• NOTE: The bonds are between
CARBONS in a parent chain, and not
hydrogens!
Structural Formula
Lewis Structure
Order of Priority
• IN A TIE, halogens get the lower number
before alkyl groups
4-chloro-2-methylpentane or
2-chloro-4-methylpentane?
Order of Priority
• IN A TIE between SIMILAR GROUPS, the
group lower ALPHABETICALLY gets the
lower number
4-bromo-2-chloropentane or
2-bromo-4-chloropentane ?
Isomers
• Straight chain alkanes:
– Alkane with straight carbon back bone
• Branched chain alkanes:
–Alkane with a branching connection of carbons.
• Isomers:
–Same molecular formula but different structures.
Only
one
possible
atom
methane (CH4) ethane (C2H6)
arrangement
propane (C3H8)
Butane (C4H10): 2 isomers
linear alkane or branched alkane
Isomers are completely different compounds.
Varied
Structures
Physical properties (MP, BP)
Types of Carbon
C C C
H
Atoms
H
C C H
• Primary carbon
– a carbon bonded to
one other carbon
(1o)
• Secondary carbon (2o)
– a carbon bonded to
two other carbons C
•
H
H
H
C C C
C C
H
H
H
H
o
C C
Tertiary carbon (3 )
H C C C
– a carbon bonded to
H C
C
C H
three other carbons
C
C C H
3
H3 CH CH CH2 CH CH3
Alkanes
C
CH
CH3
CH
H3
2
3
CH
3
Example:
Name the following compounds:
CH3
CHCH3
CH3 C CH2 CH2Br
CH2CH3
CH3
CH CH3
CH3 CH CH CH2 CH CH3
CH2CH3
CH3 C CH3
CH3
Alkanes
Example: Write the condensed
structure for the following compounds:
3,3-dimethylpentane
2-methyl-4-sec-butyloctane
1,2-dichloro-3-methylheptane
Test Your Knowledge
• http://chemed.chem.pitt.edu/Jeopardy/org
anic/index.htm