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Chemistry 11
Organic Chem Notes
Isomers
Compounds that have the same molecular formula but different molecular structures are called structural
isomers. The more C atoms there are in the formula, the more structural isomers there will be.
To determine if something is an isomer determine the molecular formula
Beginning with butane, C4H10, there is more than 1 way to arrange the atoms besides one carbon after
another.
CH3-CH2-CH2-CH3
&
CH3
|
CH3-CH-CH3
Naming Branched Alkanes
Since there are so many compounds possible it is very important to identify a particular compound by giving
it a unique name. IUPAC has proposed a set of rules to use in naming branched carbon chains.
1. Name the parent chain (longest continuous chain).
2. Identify each substituent group.
3. Number the carbons in the parent chain to give the lowest numbers to indicate the position of substituent
groups.
4. Use prefixes for groups that appear more than once. The prefix will indicate the number of times the group
appears. The Greek prefixes used are as follows:
di for two, tri for three, tetra for four, penta for five, hexa for six , hepta for seven, octa for eight
5. List the substituent groups in alphabetical order.
6. Use proper punctuations, the name is written as one word. Commas separate numbers. Hyphens are
used to separate numbers and names
The Alkene Family
The carbon-carbon bonds in the alkane family were all single covalent bonds; carbon can form multiple
covalent bonds, double or triple. Hydrocarbons containing one carbon-carbon double bond are called
alkenes. The simplest alkene must contain two carbons, the structure would be:
The Alkyne Family
Hydrocarbons containing one carbon-carbon triple bond are called alkynes. The simplest alkyne must
contain two carbons, the structure would be:
To name alkenes (double) and alkynes(triple):
1. Determine the longest continuous chain of carbons that has the double or triple bond between two
carbons. The "longest continuous chain" means through carbon – carbon bonds.
2. Number the carbons in the chain with the double or triple bond to give the lowest designated number. This
means that you have to decide whether to number beginning on the right end or left end of the chain. If it
makes no difference to the double or triple bond then shift attention to the branched groups.
3. Identify the various branching groups attached to this continuous chain of carbons by name
4. Name the branched groups as we did in the Alkane series.
5. Attach a numerical prefix indicating the lowest carbon number for the double onto the normal alkane name
but drop the "ane" ending and add the "ene" or “yne”ending associated with the Alkene or Alkyne family.
Br
|
CH3 – CH – CH2 – CH2 – CH2 – CH2 – CH3
|
Br
2,3-dibromoheptane
Halocarbon
Halocarbons are a class of organic compounds containing a
hydrocarbon parent covalently bonded with fluorine, chlorine,
bromine or iodine.
The IUPAC rules for naming halocarbons uses the same rules
as is used for Alkanes if the parent chain is saturated, or for
Alkenes or Alkynes if the parent chain is unsaturated. The halogen(s) is treated as a branched group and is
located on the continuous chain of carbons as you would locate
Aromatic Hydrocarbons
Cyclic hydrocarbons with multiple
carbon – carbon double bonds
form a special group of
compounds called aromatic
hydrocarbons. The simplest
member of this group is benzene
(C6H6). The structure of benzene
is given by:
Family
Alkane
Alkene
Alkyne
Cycloalkane
Molecular Formula
CnH2n+2
CnH2n
CnH2n-2
CnH2n
Cyclic Hydrocarbons
In some hydrocarbons the carbons at the ends of the chain join together to form a ring and are called cyclic
hydrocarbons.
Cycloalkanes are named
using the alkane parent
with the suffix cyclo. The
general formula for the
cycloalkanes is CnH2n
•
•
•
•
In naming substituted cycloalkanes:
If there is only one substituent, no number is needed. Since that ring position attached would be # 1.
If there are two substituents, the # 1 C would be listed 1st in the alphabetized list of substituent.
Number toward the 2nd substituent in the direction which gives the lower number for the carbon
bearing that second substituent and name any alkyl branch.
Alcohol
Alcohols are a family of organic compounds that share a common chemically active group called the hydroxyl
group (– O-H). Do not confuse the hydroxyl group with the hydroxide ion (OH-) (a negatively charged ion).
The hydroxyl group (– OH) represents the position in an alcohol molecule where the chemical change takes
place. The general symbol to represent any alcohol with only one hydroxyl group attached to one of its
carbons is R –OH.
Naming alcohols
Simple alcohols can be named using the common name approach of identifying and naming the alkyl portion
and follow it with the word alcohol. For example, CH3-OH could be called methyl alcohol since the CH3 group
is the methyl group. The rules for naming alcohols are as follows:
1. Identify the longest continuous (parent) chain of carbons with the hydroxyl group attached to one of the
carbons in the chain.
2. Number the chain so that the hydroxyl group is attached to the lowest numbered carbons.
3. Identify and locate the other branches on the chain so that they are
CH3
named alphabetically and their carbon number is hyphenated onto the front
|
of the name. If more than one of the same group is present use the Greek
CH3-CH-CH2-CH2-CH2-CH2-OH
prefix attached to the branch name. (di=2, tri=3, etc)
4. After all the branches have been named and located then attach the
5-methyl-1-hexanol
carbon number that is attached to the hydroxyl group onto the alkane name
associated with the number of carbons found in the parent chain in step 1.
Drop the "e" on the alkane name and attach the IUPAC ending ol to the rest of the alkane name.
Ethers
Naming ethers. (1) Name the groups (alkyl) on either side and add ether to the end.
(2) List attached alkyl groups in order of increasing size
CH3-CH2-CH2-O-CH2-CH3
(3) If they are the same the side chain is labeled “Di”
(4) Numbers are not needed to designate location of Oxygen! Ethylpropyl ether
Aldehydes and Ketones
Aldehydes are organic compounds that have a carbonyl group (–C=O) attached to the end carbon in a chain
and has the general formula, R–C=O. There is hydrogen bonded to the carbonyl carbon (double bonded
carbon).
Ketones are a part of another carbonyl family with the carbonyl group (–C=O), attached to two carbons so
that the carbonyl group is in the central part of the carbon chain. The general formula for the ketone would
be:
There are two alkyl groups, R and R', connected to the carbonyl carbon.
R'
|
To name Aldehydes, use the name of the longest carbon (parent) chain containing
R-C=O
the carbonyl group and change the –e ending to –al. C H3-CH2-CH=O is propanal
To name Ketones, use the name of the longest carbon (parent) chain containing the carbonyl group and
change the –e ending to –one.
O
║
is propanone
CH3-C-CH3
Carboxylic Acid Family
The Carboxylic Acid Family is a family of organic compounds with the functional group being the carboxyl
group, –COOH. This group is attached to one of the carbons in the rest of the molecule. The carboxyl group
is actually a carbonyl group, C=O, bonded to a hydroxyl group, –OH. Taking the first four letters of the
word carbonyl and the last four letters of the word hydroxyl you get the word carboxyl.
To name carboxylic acids
1. Determine the longest continuous chain of carbons that have the Carbonyl carbon as part of the
continuous chain.
2. Number the carbons in the chain beginning with the carbonyl carbon as the C-1 carbon.
3. Identify the various branching groups attached to this continuous chain of carbons by name and
name the branched groups as we did before.
4. If it is a saturated acid use the normal alkane name corresponding to the number of carbons in the
continuous chain. If it has an unsaturated center that is a double bond then use the alkene name and
prefix the name with the lowest carbon involving the double bond. If a triple bond is involved then use
the alkyne name and prefix the name with the lowest carbon number involving the triple bond
5. Drop the last “e” in "ane", "ene", or "yne" ending and add the IUPAC ending for this family which is
"oic acid".
CH3-CH2-CH2-CH2-CH2-COOH Hexanoic Acid
CH3-CH2-CH2-COOH
|
CH3
2-methylbutanoic acid