Topic 10.1
1 2 3 4
H O N C

What is organic chemistry?
• study of carbon, the compounds it makes, and the reactions it undergoes
• over 16 million carbon-containing compounds are known
• because the C-C single bond (348 kJ mol -1 ) and the C-H bond (412 kJ mol -1 ) are strong, carbon compounds are stable
• carbon can form chains and rings

Empirical, molecular & structural formulas
2

• empirical formula
– simplest ratio of atoms in a molecule
• molecular formula
– actual numbers of atoms in a molecule
Empirical
Formula
Molecular
Formula
CH
4
CH
3
CH
2
O
CH
2
CH
2
CH
4
C
2
H
6
C
6
H
12
O
C
C
4
8
H
H
8
16
6

structural formula
• unambiguously shows how the atoms are bonded together
• can use condensed structural formulas
– bonds are omitted, repeated groups put together , side chains put in brackets
• CH
• CH
3
3
CH
2
CH
CH
2
CH
– or even CH
(CH
3
2
CH
3
(CH
) CH
2
2
CH
3
2
)
CH
3
4
CH
3

condensed

skeletal formula
– not accepted in the IB for answers but often
– every “corner” represents a carbon
– hydrogens are implied

• (structural) isomers: compounds with the same molecular formula but different structure
(arrangement of atoms)

• different isomers are different compounds
• have different physical properties such as melting point and boiling point

Structural
Formulas for C
4
H
10
O
Isomers

• related compounds that have the same
functional group ( groups of atoms found within molecules that are involved in the chemical reactions characteristic of those molecules)

• differ from each other by a CH
2 unit
• can be represented by a general formula
– examples:
• C n
H
2n+2
(alkanes) or C n
H
2n
(alkenes) or…

• have similar chemical properties
• have physical properties that vary in a regular manner as the number of carbon atoms increases
– Example: the alkanes

•
•
Trends in boiling points of members of a homologous series melting point and boiling point increase with more carbon atoms
Why?
– intermolecular forces increase
– adding a CH
2 adds more electrons
• this increases the
London dispersion forces
Alkane Formula Boiling
Pt./ o C methane CH
4 ethane C
2
H
6 propane C
3
H
8 butane
C
4
H
10
-162.0
-88.6
-42.2
-0.5

Structural formulas for the isomers of noncyclic alkanes up to C
6
• hydrocarbon chains where all the bonds between carbons are SINGLE bonds
• C n
H
2n+2
• draw out and write the structural formulas for all isomers that can be formed by:
– CH
4
–
– C
3
–
C
– C
4
– C
5
C
2
6
H
H
H
H
H
6
8
10
12
14
Richard Thornley
2:54

Naming the isomers (IUPAC) of non-cyclic alkanes up to C
6
1.
Richard Thornley 3:35
2. Determine the longest carbon chain
– Use the prefix to denote the number carbons
1 M eth-
2 E th-
3 P rop-
4 B ut-
5 Pent-
6 Hex-
Monkeys
Eat
Peeled
Bananas

3. use the suffix “-ane” to indicate that the substance is an alkane
4. number the carbons in the chain consecutively, starting at the end closest to a substituent
(groups attached to the main chain)…”most busy end”

5. name and number the location of each substituent
– the name of the substituent will be written before the main chain and will end with “–yl” (or just memorize the below)
• CH
3
• C
2
H
5 is methyl is ethyl
• C
3
H
7 is propyl
And with 2 or more side chains:
5. use prefixes di-, tri-, tetra-, to indicate when there are multiple side chains of the same type
6. use commas to separate numbers and hyphens to separate numbers or letters.
7. name the side chains in alphabetical order

• How about C
5
H
12
? The isomers are:
Pentane 2-methyl-butane 2,2-dimethyl propane

Nomenclature Practice
Name this compound
CH
3
H
3
C
1
2
3
4
Cl
5
6
7
H
3
C
9
8
CH
3
9 carbons = nonane
Step #1: For a branched hydrocarbon, the longest continuous chain of carbon atoms gives the root name for the hydrocarbon

Nomenclature Practice
Name this compound
CH
3
H
3
C
1
2
3
4
Cl
5
6
7
H
3
C
9
8
CH
3
9 carbons = nonane
CH
3
= methyl chlorine = chloro
Step #2: When alkane groups appear as substituents, they are named by dropping the -ane and adding -yl .

Nomenclature Practice
Name this compound
CH
3
H
3
C
1
2
3
4
Cl
1
5
6
7
H
3
C
9
8
CH
3
9 NOT 9
9 carbons = nonane
CH
3
= methyl chlorine = chloro
1
Step #3: The positions of substituent groups are specified by numbering the longest chain of carbon atoms sequentially, starting at the end closest to the branching.

Nomenclature Practice
Name this compound
CH
3
H
3
C
1
2
3
4
Cl
5
6
7
H
3
C
9
8
CH
3
9 carbons = nonane
CH
3
= methyl chlorine = chloro
2 -chloro3 , 6 -dimethylnonane
Step #4: The location and name of each substituent are followed by the root alkane name. The substituents are listed in alphabetical order (irrespective of any prefix), and the prefixes di-, tri-, etc. are used to indicate multiple identical substituents
.

Structural formulas for the isomers of the straight chain alk enes up to C
6
• alkenes have a double bond between two or more of the carbons
• C n
H
2n
• draw out and write the structural formulas for all isomers that can be formed by each
Richard Thornley 10.1.7 (1:37)
– C
2
H
4
– C
3
H
6
– C
4
H
8
– C
5
H
10
– C
6
H
12

Naming the isomers (IUPAC) of straight chain alk enes up to C
6
1. suffix changes to “-ene”
2. when there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number
3. begin counting the carbons closest to the end with the C=C bond
– numbering the location of the double bond(s) takes precedence over the location of any substituents
1-butene 2-butene but-1-ene but-2-ene

CH
2
CH
3
CH
2
C
CH
CH
2
C
2
CH
3
CH
3
CH
3

CH
2
CH
3
CH
2
C
CH
CH
2
C
2
CH
3
CH
3
CH
3
ene

CH
2
CH
3
CH
2
C
CH
CH
2
C
2
CH
3
CH
3
CH
3
ene

1
2 3
5
4
6
ene

1
2 3
5
4
6
ene

ethyl
1 5 6
2 3 4 methyl methyl

ethyl
1 5 6
2 3 4 methyl methyl
1-hexene

ethyl
1 5 6
2 3 4 methyl methyl
2-ethyl-4-methyl-4-methyl-1-hexene

ethyl
1 5 6
2 3 4 methyl methyl group similar branches

CH
3
CH propene
CH
2
CH
3
CH
3
CH
3
CH CH C CH
3
CH
3
CH CH CH
3
2-butene
2,4-dimethyl-2-pentene
2,4-dimethyl pent-2-tene

CH
3
CH
2
CH C CH
2
CH
3
CH
3 a) 3,3-dimethyl-1-pentene
CH
3
CH
3
C CH CH
2
CH
2
CH
3 b) same
CH
3
CH
3
C C CH CH CH
3
CH
3 c) 4,5 dimethyl-2-hexene