Fundamentals of Organic ChemistryTopic 10.1

HONC

1 2 3 4 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 number of each atom in a molecule

Empirical Formula

Molecular Formula

CH4 CH4

CH3 C2H6

CH2O C6H12O6

CH2 C4H8

CH2 C8H16

structural formula• unambiguously shows how the atoms are

bonded together

condensed structural formulas – bonds are omitted, repeated groups put

together, side chains put in parenthesis• 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 vertex or end 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 compounds

• have different physical properties such as melting 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

Alkane Formula Boiling Pt./oC

methane CH4 -162.0

ethane C2H6 -88.6

propane C3H8 -42.2

butane C4H10 -0.5

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

• therefore the chain is said to be saturated with hydrogen

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

– CH4 C2H6 C3H8 C4H10 C5H12 C6H14Richard Thornley

2:54

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

Alkanes

1. Richard Thornley 3:35

2. Determine the longest carbon chain

– Use the prefix to denote the number carbons

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

1 Meth-

2 Eth-

3 Prop-

4 But-

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

– alkyl groups are the simplest substituents (yl ending)

• CH3 is methyl

• C2H5 is ethyl

• C3H7 is propyl

• C4H9 is butyl

6. use prefixes di-, tri-, tetra-, to indicate when there are multiple side chains of the same type

7. use commas to separate numbers and hyphens to separate numbers or letters.

8. name the side chains in alphabetical order

• How about C5H12? The isomers are:

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

Nomenclature 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 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 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 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 straight chains

• alkenes have a double bond between two or more of the carbons (alkynes have a triple bond)

• the carbons are unsaturated, not as many hydrogensbecause double bonds are present

• CnH2n

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

– C2H4

– C3H6

– C4H8

– C5H10

– C6H12

Alkenes and Alkynes

Richard Thornley 10.1.7 (1:37)

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http%3A%2F%2Fstaff.jccc.net%2Fpdecell%2Fbiochemistry%2Ftriglyc.html&ei=hxVUVZjbIIbBsAW8koGICg&psig=AFQjCNHTvVO_mwDZ0aQ3dEKyKFs9AEw54g&ust=1431660285510819

1. suffix changes to “-ene” for alkenes and “-yne” for alkynes

2. when there are 4 or more carbon atoms in a chain, the location of the double/triple bond is indicated by a number

3. begin counting the carbons closest to the end with the double or triple bond– numbering the location of the multiple

bonds takes precedence over the location of any substituents

but-1-ene but-2-ene methyl propene

Naming the isomers (IUPAC) of straight chain alkenes or alkynes 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-hexeneene

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-hexene1-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

methyl

attach 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 hex-1-ene

ethyl

methyl

methyl

but-2-ene

propene

CH3 CH CH2

CH3 CH CH CH3

CH3 CH CH C

CH3 CH3

CH3

2,4-dimethyl pent-2-tene

b) same

c) 4,5 dimethyl hex-2-ene

a) 3,3-dimethyl pent-1-ene

CH2 CH C CH2 CH3

CH3

CH3

CH3 C CH CH2

CH3

CH2 CH3

CH CH CH3

CH3

CC

CH3

CH3