organic chemistry(ex: methane, propane, etc.) 2. number the chain consecutively, starting at the end...
TRANSCRIPT
Organic Chemistry
Nomenclature:
Alkanes
Alkanes
• Hydrocarbon chains where all the bonds
between carbons are SINGLE bonds
• Name uses the ending –ane
• Examples: Methane, Propane, Butane,
Octane, 2-methylpentane
• For straight chain hydrocarbons. The prefix indicates
the number of carbon atoms.
• The suffix -ane is added to designate that the
compound is an alkane
• General Formula: CnH2n+2
Naming Alkanes
Prefixes for # of Carbons
1 Meth 6 Hex
2 Eth 7 Hept
3 Prop 8 Oct
4 But 9 Non
5 Pent 10 Dec
• Alkenes have one (or more) carbon to carbon double bonds
• When there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number.
• Numbering the location of the double bond(s) takes precedence over the location of side chains
• General Formula: CnH2n
Alkenes
1 butene 2-butene methylpropene
• Alkenes have one (or more) carbon to carbon triple bonds
• When there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number.
• Numbering the location of the triple bond(s) takes precedence over the location of side chains
• General Formula: CnH2n-2
Alkynes
1 butene 2-butene methylpropene
• For branched chain hydrocarbons, identify the longest
consecutive (straight) chain first. Then name the side
chains or branches.
• The name of the branches end in “yl” and go before
the name of the straight chain
Naming Alkanes with
branched chains
-methylpropane
methyl butane
dimethyl propane
Summary: IUPAC Rules for Branched
Alkane Nomenclature
1. Find and name the longest continuous carbon chain. This is called the parent chain. (Ex: methane, propane, etc.)
2. Number the chain consecutively, starting at the end nearest an attached group (alkyl or 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?
Step 2. Number the parent chain.
• Number the parent chain so that the
attached groups are on the lowest
numbers
1 2 3 4 5
Methyl is on carbon #2 of the parent chain
5 4 3 2 1
Methyl is on carbon #4 of the parent chain
GREEN is the right
way for this one!
1 2
3 7 8
4 5 6
8 7
6 2 1
5 4 3
Groups on 2, 3, and 5
Groups on 4, 6, and 7
1 2 3 4 5 6
7
Groups on 2 and 5
7 6 5 4 3 2
1
Groups on 3 and 6
Step 3. Name the attached groups.
• Carbon (alkyl) groups: – Methyl CH3 -
– Ethyl CH3CH2-
– Propyl CH3CH2CH2 – (if connected by center carbon, it is ISOPROPYL)
• Substituents: (we’ll discuss later) – Halogens
• Fluoro (F-)
• Chloro (Cl-)
• Bromo (Br-)
• Iodo (I-)
– Functional Groups
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.
1 2 3 4 5
2-methyl
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
2-methyl pentane
5-ethyl, 2,3-dimethyl octane
5-isopropyl-2-methyl heptane
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!
Condensed
Structural Formula Lewis Structure
Draw Some Simple Alkanes
• 2-methylpentane
• 3-ethylhexane
• 2,2-dimethylbutane
• 2,3-dimethylbutane
Types of Carbon Atoms
• Primary carbon (1o)
– a carbon bonded to
one other carbon
• Secondary carbon (2o)
– a carbon bonded to
two other carbons
• Tertiary carbon (3o)
– a carbon bonded to
three other carbons
C
C
C
C
H
H
H
C C
H
H
C
C
C
H
C
C
C
C
H
H
H
C C
H
H
C
C
C
H
C
C
C
C
H
H
H
C C
H
H
C
C
C
H
C
C
C
C
H
H
H
C C
H
H
C
C
C
H
Isomers
• Straight chain alkanes: An alkane that has all its carbons connected in a row.
• Branched chain alkanes: An alkane that has a branching connection of carbons.
• Isomers: Compounds with same molecular formula but different structures.
• There is only one possible way that the
carbons in methane (CH4), ethane (C2H6),
and propane (C3H8) can be arranged.
• However, carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane.
•Different isomers are completely different
compounds. They have different structures,
different physical properties such as melting point
and boiling point, and may have different
physiological properties.
Learning Check
• Draw all possible structural isomers of C5H12
Alkanes
Example: Name the following compounds:
CH3
CH3CH(CH
3)2CH
2CH
2Br
CH3
CH CH CH2
CH CH3
CH2CH
3C
CH
CH3
CH3
CH3
CH3
CH3
C CH2
CH2Br
CHCH3
CH2CH
3
CH3
CH3
CH CH CH2
CH CH3
CH2CH
3C
CH
CH3
CH3
CH3
CH3
CH3
Alkanes
Example: Write the condensed
structure for the following compounds:
3,3-dimethylpentane
4-sec-butyl-2-methyloctane
1,2-dichloro-3-methylheptane
Naming Compounds With
Functional Groups • Various functional groups have unique suffixes that
designate the functional group.
• The functional group takes precedence in
numbering the carbon chain.
• Branches to the carbon chain are named in the
usual manner.
alcohols “ol” Amides “amide”
Aldehydes “al” Amines “amine” or amino as a prefix
Ketones “one” Ethers Ethoxy as prefix
Acids “oic” halohydrocarbons Fluoro, bromo, chloro or
iodo
Esters “oate” 27
Alcohols
Suffix = “ol” 1- Propanol
2- Propanol
2-methyl-2-propanol
28
Suffix = “al”
Propanal
Note that the
aldeyhde group is
always on an end
carbon or carbon 1
Aldehydes
29
Suffix = “one”
Propanone
(also known as acetone)
Butanone
(also known as methyl ethyl ketone)
2-Pentanone
(note the number is necessary
Because the C=O could be on carbon
2 or carbon 3)
Ketones
30
Suffix = “oic”
Butanoic acid
Note that the acid group
(called a “carboxyl”) is
always on an end carbon
or carbon 1
Carboxylic Acids
31
Suffix = “oate”
Ethyl butanoate
Butyl ethanoate
There are two branches. The
branch with the carbonyl gets
the suffix
Esters
32
Suffix = “amide”
butanamide
Note that the amide group is
always on an end carbon or
carbon 1
Amides
33
Suffix = “amine”
Or prefix = “amino”
Propylamine or 1-aminopropane
2-propylamine or 2-aminopropane
2-methyl-2-propylamine or
2-methyl -2- aminopropane
Amines
34
prefixes = “fluoro,
chloro, bromo,
iodo”
1-bromopropane
2 chlorobutane
1,2 diiodoethane
Cis 1,2difluroethene
Trans 1,2 difluoroethene
1,1,2 trifluorothene
Halohydrocarbons
35
Suffix = “oxy”on first branch
Ethoxyethane
(diethylether)
Ethoxybutane
(ethylbutyl ether)
Ethers
36
Aromatic Compounds With
Functional Groups
Benzoic acid
2 hydroxybenzoic acid
3 bromobenzoic acid
37
Nitriles
38
Nitriles have a cyanide group. The
name is based on the longest carbon
chain that includes the carbon atom in
the nitrile group.
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 ?