Transcript organic chemistry

Chapter 22 Notes, part I
Organic Chemistry
Organic Chemistry
• Chemistry of carbon
containing compounds is
organic chemistry.
• The name is derived from the
fact that early scientists
thought carbon compounds
could only be synthesized by
organisms.
Bob LOVES organic chemistry.
Hydrocarbons
• Organic chemistry centers
around hydrocarbons—
compounds made of carbon
and hydrogen only.
• Hydrocarbons are found all
around us, especially in the
petroleum industry.
Bob thinks understanding hydrocarbons is
a bright idea!
Alkanes
• Alkanes are hydrocarbons
where all the carbons are
attached to each other with
single bonds.
• A straight chain alkane has
all carbons in a row (no
branches).
Bob jumps for joy because alkanes are
grrrreat!
Naming straight chain alkanes
• Ten prefixes are needed for
naming most common alkanes:
Meth- =1
hex=6
Eth=2
hept=7
Prop=3
oct=8
But=4
non=9
Pent=5
dec=10
Now Bob is sad…
…he only has six toes
to count with!
Naming straight chain alkanes
• First, count the number of
carbons in the chain.
• Second, start the name with
the prefix for that many
carbons and end it in –ane.
Branch chain alkanes and alkyl groups
• Not all alkanes are in a straight line!
• Anything that is attached where
hydrogen is usually located is called
a substituent. A hydrocarbon
substituent is called an alkyl group.
Name
Formula
• Methane
CH4
• Ethane
C2H6
• Propane
C3H8
•
•
•
•
•
•
•
C4H10
C5H12
C6H14
C7H16
C8H18
C9H20
C10H22
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Structure
Naming branch chain alkanes
• First, name the alkyl group
coming off of the main chain.
Give the prefix for the
number of carbons, then end
it in –yl.
• Then name the main chain,
ending just like before in –
ane.
Oh boy, Bob’s going to have to
study this!
Naming branch chain alkanes
• If there is more than one place to
put an alkyl group, you have to put
a number before it to signify its
location.
• Number from the end that gives you
the lowest overall number.
• If there is more than one alkyl
group, put a prefix to show how
many there are (di, tri, tetra, etc.)
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
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
Groups on 2, 3, and 5
Groups on 4, 6, and 7
1
7
2
6
3
5
4
4
Groups on 2 and 5
5
3
6
72
1
Groups on 3 and 6
Name the attached groups.
• Carbon (alkyl) groups
– Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –
• Halogens
– Fluoro (F-)
– Chloro (Cl-)
– Bromo (Br-)
– Iodo (I-)
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
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
• 2-methylpropane
• 2,3,3triMethylPentane
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 ?
Just remember, Bob loves you!