Isomers & Physical properties of alcohols

The slides contains Introduction to Isomerism Topic, classification of Isomers,Physical Properties of Alcohols. It contains examples and questions.

1. Alcohols Isomerism & Physical Properties D.M S.J K.M

2. Contents Introduction: Learning Objectives What is Isomerism Isomerism in Hydrocarbons & Classification Alcohols Isomerism Examples and Questions 2 Physical Properties

3. Introduction: Learning Objectives What is Isomerism 2. Review İsomerism in Hydrocarbons ; 3. Understand İsomerism in Alcohols ; 4. Determine Physical Properties of Alcohols ; 1. Identify İsomers ; 5. Explain why boiling points of alcohols are higher than alkanes, ethers etc. ; 6. Discuss the factors that are affect to the physical properties of alcohols ;

4. What is Isomerism ? Similarities Differences Flashback: Isomerism in Hydrocarbons Car Parts: Tire, Windows, etc. Different Characteristics Isomers are compounds with the same chemical formulas but different structures and therefore, properties

5. Isomers Classification of isomers: Constitutional isomers Chain isomerism Position isomerism Functional group isomerism Isomers of alcohols: Ethers Structures of ethers Isomerism in Hydrocarbons & Classification

6. Butane 2-methylpropane Chain Isomers C 4 H 10 C 4 H 10 Isomerism in Hydrocarbons & Classification

7. Structural isomers are compounds that have the same molecular formula and different connectivity . Website https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Fundamentals/Isomerism_in_Organic_Compounds/Structural_Isomerism_in_Organic_Molecules Structural (Constitutional) Isomers

8. Alcohols Isomerism

9. 9 Chain Isomerism 2-Methyl-1-propanol 1-butanol

10. More Examples: Chain isomers C 4 H 10 O

11. 11 Position Isomerism 2-Propanol 1-Propanol

12. More Examples: Position isomers C 5 H 12 O

13. 13 Functional Isomerism Dimethyl Ether Ethanol 3

14. More Examples: Functional isomers C 4 H 10 O C 3 H 8 O

15. Isomers of alcohols: Ethers R-O-R’ C n H 2n+2 O

16. Let’s practice: Draw and classify structural isomers of C 4 H 10 O (Homework) Draw and classify structural isomers of C 5 H 12 O

17. C 5 H 12 O :

18. Physical Properties: Intermolecular vs Intramolecular Forces

19. 1. Van der Waals forces: Dipole-dipole forces London dispersion forces Intermolecular Forces: 2. Hydrogen bonds Intramolecular Forces: Covalent bonds: Non-polar covalent bonds Polar covalent bonds Ionic bonds Metallic bonds

20. C 5 H 12 O Pentan-1-ol 2,2-dimethyl propan-1-ol Isomers  are compounds whose  properties  are  different  because their atoms are bonded together in  different  arrangements. Example: Boiling point = 138 °C Boiling point = 113,5 °C Physical Properties of Isomer Alcohols

21. A  straight - chain  alkane will  have  a  boiling point higher  than a branched- chain  alkane due to the greater surface area in contact, thus the greater van der Waals forces, between adjacent molecules.

22. The boiling points of the alcohols increase as the number of carbon atoms increases. Ether molecules have no hydrogen atom on the oxygen atom (that is, no OH group). Therefore there is no intermolecular hydrogen bonding between ether molecules, and ethers therefore have quite low boiling points for a given molar mass.

23. Solubility in water: Alcohols Ethers

24. Classification

25. Condensed Structural Formula Name Molar Mass Boiling Point (°C) Intermolecular Hydrogen Bonding in Pure Liquid? C 2 H 6 O CH 3 OCH 3 dimethyl ether 46 –25 no CH 3 CH 2 OH ethyl alcohol 46 78 yes C 4 H 8 O CH 3 CH 2 OCH 2 CH 3 diethyl ether 74 35 no CH 3 CH 2 CH 2 CH 2 OH butyl alcohol 74 117 yes

26. Formula Name Solubility in Water (g/100 g) CH 3 OH methanol infinitely soluble CH 3 CH 2 OH ethanol infinitely soluble CH 3 (CH 2 ) 2 OH propanol infinitely soluble CH 3 (CH 2 ) 3 OH butanol 9 CH 3 (CH 2 ) 4 OH pentanol 2.7 CH 3 (CH 2 ) 5 OH hexanol 0.6 CH 3 (CH 2 ) 6 OH heptanol 0.18 CH 3 (CH 2 ) 7 OH octanol 0.054 CH 3 (CH 2 ) 9 OH decanol insoluble in water Solubilities of Alcohols in Water

27. Methanol vs Ethanol Ethanol and methanol are liquids that sound the same and have many of the same physical characteristics including look and smell. 2. Ethanol is safe to consume in moderate amounts and is found in all alcoholic beverages whereas methanol should be avoided at all costs as even a small dose can cause blindness or death. 3. Ethanol is used for alcohol, cleaning, solvents, and fuels, and while methanol is also found in solvents and fuels, it is primarily used to make other chemicals.

28. Difference between Ethanol and Methanol Ethanol is a type of alcohol with its carbon skeleton consisting of an ethyl ring. Methanol consists of in its carbon bond methyl group. Ethanol is a poor acid compared with water, in terms of acidity. Methanol has higher acidity than liquids. Ethanol has a heavy, burning smell and emits bright blue flame. Methanol is unpredictable and has a characteristic odour. When burning it gives off light white flame. Ethanol is typically prepared by the fermentation of food crops from factories. Methanol is manufactured mainly by synthetic processes. Ethanol is the primary ingredient of alcoholic beverages. Since methanol is highly poisonous it is not appropriate for use at all. Generally used in the manufacturing of products such as formaldehyde etc.

29. Let’s practice: Which one of the following compounds is an isomer of CH 3 CH 2 CH 2 CH 2 OH? (a) CH 3 CH 2 CH 2 OH (b) CH 3 CH(OH)CH 3 (c ) CH 3 CH 2 CH 2 OCH 3 (d) CH 3 CH 2 CH 2 CH 3 (e) none of the above

30. Let’s practice: Which one of the following alcohols would have the lowest boiling point ? (a) butanol (b) ethanol (c ) 2-methyl 2-butanol (d) propanol

31. Let’s practice: An alcohol has a higher boiling point than an alkane with the same length carbon chain. True or false? a)  True b)  False

32. Draw and classify structural isomers of C 6 H 14 O Using Alcohol Worksheet (jpeg) identify chain and position isomers