Organic Chemistry

Topic 10.1

HONCC

1 2 3 44 bonds

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 Empirical FormulaFormula

MoleculaMolecular r

FormulaFormula

CHCH44 CHCH44

CHCH33 CC22HH66

CHCH22OO CC66HH1212OO66

CHCH22 CC44HH88

CHCH22 CC88HH1616

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• CH3CH2CH2CH2CH2CH3

–or even CH3(CH2)4CH3 • CH3CH(CH3) CH2CH3

condensed

skeletal formula– not accepted in the IB for answers but

often used in questions– every “corner” represents a carbon– hydrogens are implied

Isomers• (structural) isomers: compounds with

the same molecular formula but different structure (arrangement of atoms)

• different isomers are different compoundsifferent isomers are different compounds• have different physical properties such as have different physical properties such as

melting point and boiling pointmelting point and boiling point

Structural Formulas

for C4H10O Isomers

Homologous series/compounds• 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 CH2 unit• can be represented by a general

formula– examples:

• CnH2n+2 (alkanes) or CnH2n (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 CH2 adds

more electrons• this increases the

London dispersion forces

AlkaneAlkane FormulFormulaa

Boiling Boiling Pt./Pt./ooCC

methanmethanee

CHCH44 -162.0-162.0

ethaneethane CC22HH66 -88.6-88.6

propanpropanee

CC33HH88 -42.2-42.2

butanebutane CC44HH1010 -0.5-0.5

• hydrocarbon chains where all the bonds between hydrocarbon chains where all the bonds between carbons are SINGLE bondscarbons are SINGLE bonds

• CnH2n+2

• draw out and write the structural formulas for all isomers that can be formed by: – CH4

– C2H6 – C3H8

– C4H10

– C5H12

– C6H14

Richard Thornley 2:54

Structural formulas for the isomers of non-cyclic alkanes up to C6

Alkanes

1. Richard Thornley 3:352. Determine the longest carbon chain

– Use the prefix to denote the number carbons

Naming the isomers (IUPAC) of non-cyclic alkanes up to C6

11 MMeth-eth-

22 EEth-th-

33 PProp-rop-

44 BBut-ut-

55 Pent-Pent-

66 Hex-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)

• CH3 is methyl

• C2H5 is ethyl

• C3H7 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 type6. use commas to separate numbers and

hyphens to separate numbers or letters.7. name the side chains in alphabetical order

• How about C5H12? The isomers are:

Pentane 2-methyl-butane 2,2-dimethyl propane

Nomenclature PracticeNomenclature Practice

CH3 CH3

CH3

CH3

Cl

Name this compound

Step #1: For a branched hydrocarbon, the longest continuous chain of carbon atoms gives the root name for the hydrocarbon

152 43

9

6

87

9 carbons = nonane

Nomenclature PracticeNomenclature PracticeName this compound

CH3 CH3

CH3

CH3

Cl

152 43

9

6

87

9 carbons = nonane

Step #2: When alkane groups appear as substituents, they are named by dropping the -ane and adding -yl.

CH3 = methyl

chlorine = chloro

Nomenclature PracticeNomenclature PracticeName this compound

CH3 CH3

CH3

CH3

Cl

152 43

9

6

87

9 carbons = nonane

CH3 = methyl

chlorine = chloro

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.

1 9 NOT 9 1

Nomenclature PracticeNomenclature PracticeName this compound

CH3 CH3

CH3

CH3

Cl

152 43

9

6

87

9 carbons = nonane

CH3 = methyl

chlorine = chloro

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.

2-chloro-3,6-dimethylnonane

Structural formulas for the isomers of the straight chain alkenes up to C6

• alkenes have a double bond between two or more of the carbons

• CnH2n

• draw out and write the structural formulas for all isomers that can be formed by each

– C2H4

– C3H6

– C4H8

– C5H10

– C6H12

Alkenes

Richard Thornley 10.1.7 (1:37)

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-butenebut-1-ene but-2-ene

Naming the isomers (IUPAC) of straight chain alkenes up to C6

ene

Naming Practice!!!

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

choose the correct ending

ene

determine the longest carbon chain with the double bond

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

assign numbers to each carbon

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

ene

assign numbers to each carbon

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

ene

1-hexene ene

attach prefix (according to # of carbons)

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

determine name for side chains

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

1-hexene 1-hexene

ethyl

methyl

methyl

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

2-ethyl-4-methyl-4-methyl-1-hexene

ethyl

methyl

methylattach name of branches alphabetically

group similar branches

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

2-ethyl-4-methyl-4-methyl-1-hexene

ethyl

methyl

methyl

group similar branches

CH3 CH2 C

CH2

CH2 C

CH2

CH3

CH3

CH3

CH3 CH2 C2

CH21

CH23

C4

CH25

CH3

CH3

CH36

2-ethyl-4,4-dimethyl-1-hexene

or 2-ethyl-4,4-dimethyl hex-1-ene

ethyl

methyl

methyl

2-butene

propene

CH3 CH CH2

CH3 CH CH CH3

CH3 CH CH C

CH3 CH3

CH3

2,4-dimethyl-2-pentene2,4-dimethyl pent-2-tene

b) same

c) 4,5 dimethyl-2-hexene

a) 3,3-dimethyl-1-pentene

CH2 CH C CH2 CH3

CH3

CH3

CH3 C CH CH2

CH3

CH2 CH3

CH CH CH3

CH3

CC

CH3

CH3