1. 5.2.0 Homologous Series
Chemical Families

2. Like families they have things in common but they are not identical
All the members of each homologous series have 5 things in common

3. 1. Same General Formula Alkenes CnH2n Alkynes CnH2n-2
e.g. Alkanes are CnH2n+2
[n is any whole number greater than 0] This is an alkane
CH4 ; C2H6 ; C3H8 ; C4H10 etc
Alkenes CnH2n
Alkynes CnH2n-2
Alcohols CnH2n+1OH

4. 2. Differ by CH2
Diagrams of methane ethane and propane

5. 3. Same Functional Group Functional Group is The group of atoms
that gives the Homologous Series
its main characteristics [or properties.]

6. 1. Alkane C

7. 2. Alkene C

8. 3. Alkyne C

9. 4. Alcohol C OH

10. 5. Aldehyde C O H

11. 6. Ketone C O C

12. 7. Carboxylic Acid C O OH

13. 8. Ester O C C O C

14. 4. Similar Chemical Properties
Their chemical properties are similar
NOT the same
Their properties change gradually
As the carbon chain gets longer they tend to become less reactive

15. 5. Similar Physical Properties
Their physical properties change gradually
E.g. Melting Point, Boiling Point, solubility, density, viscosity
As the carbon chain gets longer their MP and BP get higher, density increases, solubility decreases, viscosity increases

16. Test What five things do homologous series have in common? [5]
What happens to (a) BP and (b)MP and (c) reactivity (d) solubility as the carbon chain gets longer chain gets longer? [4]
Give the functional group of the following series (a) aldehydes (b) alkenes (c) alkynes (d) alcohols (e) carboxylic acids [5]
Give the general formula a) aldehydes (b) alkenes (c) alkynes (d) alcohols [5]
What is a functional group? [2]

17. Test
What five things do homologous series have in common? [5] same general formula / differ by CH2 / same functional group / similar chemical and / physical properties
What happens to (a) BP and (b)MP and (c) reactivity (d) solubility as the carbon chain gets longer ? [4] up / up / down / down
Give the functional group of the following series (a) aldehydes (b) alkenes (c) alkynes (d) alcohols (e) carboxylic acids [5] –CHO / C=C- / -C≡C -/ -OH /-COOH

18. Give the general formula a) aldehydes (b) alkenes (c) alkynes (d) alcohols [4] CnH2n+1CHO / n = 0 or whole number / CnH2n / CnH2n-2 / CnH2n+1OH
What is a functional group? [2] Group of atoms / gives main characteristics