1. Alkanes, alkenes, alcohols, aldehydes and ketones
Organic Chemistry
Alkanes, alkenes, alcohols, aldehydes and ketones

2. Part 1: Types of Hydrocarbons
Hydrocarbons contain C and H
There are 4 families, alkanes only have C-C single bonds, alkenes have at least one C=C and alkynes have a least one CΞC bond, aromatics are like cyclohexane with 3 C=C double bonds

3. Nomenclature for Alkenes
Alkenes have one or more C=C
Step 1: Name the longest chain with the C=C in it
Step 2: Number the longest chain so that the carbons in the C=C have the lowest numbers
Step 3: Locate the lowest numbered C in the C=C
Step 4: Locate and name attached groups
Step 5: Combine the names

4. Naming Alkenes 2 carbons prefix eth- 1 C=C suffix –ene Name = ethene
3 carbons prefix prop-
1 C=C suffix –ene
Name = propene
4 carbons prefix but-
1 C=C suffix –ene
Name = butene
But where is the C=C?
1 butene (or but-1-ene)
2 butene (or but-2-ene)

5. Naming Cycloalkenes 6 carbons prefix hex- 1 C=C suffix –ene
Name = hexene
6 carbons in a ring
cyclohexene
5 carbons prefix hex-
1 C=C suffix –ene
Name = pentene
6 carbons in a ring
cyclopentene

6. Naming Alkynes 2 carbons prefix eth- 1 CΞC suffix –yne Name = ethyne
3 carbons prefix prop-
1 CΞC suffix –yne
Name = propyne
4 carbons prefix but-
1 CΞC suffix –yne
Name = butyne
But where is the CΞC?
1 butyne (or but-1-yne)
2 butyne (or but-2-yne)

7. Aromatics Aromatics contain This is called benzene
This is called toluene (methyl benzene)

8. Identifying the type of hydrocarbon
Alkanes, alkenes, alkynes and aromatics have different chemical properties and we can identify what we have by performing 3 tests
Reaction with O2 (combustion)
Reaction with Br2 (Bromine test)
Reaction with KMnO4 (Potassium Permanganate test)

9. Reaction with O2 (combustion)
All hydrocarbons react with O2 to make CO2 (with some CO and C) and H2O
CH4 + 2O2  CO2 + 2H2O
(one CO2 for every C and one H2O for every 2H)
If all hydrocarbons react how can this tell us if we have an alkane, alkene, alkyne or aromatic?
Heavier hydrocarbons (more C) don’t evaporate as easily so less easy to combust
Alkynes, Aromatics and cycloalkanes and cycloalkenes burn with sooty flames
Ethyne (acetylene)
aromatic
methane
cyclohexene

10. Reaction with Br2 (Bromine test)
Add
alkane or alkene
Alkane
Alkene
Alkenes and alkynes quickly react with Br2 to make haloalkanes (colorless)
Alkanes don’t react (except slowly in bright light)
Benzene doesn’t react toluene will
Br2 water

11. Reaction with KMnO4 (Baeyer test)
In this test KMnO4 (purple) reacts with alkenes but not alkanes or aromatics
Alkane or aromatic (negative test)
Alkene (positive test)
alkene
diol

12. The Experiment (Done individually)
You will each receive an unknown hydrocarbon which you will identify by noting how it behaves in a series of tests and compare it to how certain known compounds behave in those same tests.
In each case write out the balanced chemical reactions for the knowns and the unknowns
Br2 Test: In the fume hood a 3-4 drops Br2/CH2Cl2 solution to 5 drops of hexane, 1-hexene, toluene and your unknowns, record observations. You can leave it out to see if it changes in light for 10 mins. Write out equations
Combustion Test: In fume hood combust 5-10 drops of hexane, 1-hexene, toluene and your unknown, in an evaporating dish record observations, write out equations
Baeyer Test: To 5 drops of hexane, 1-hexene, toluene and your unknown add 15 drops of 1% KMnO4 record your observations
From your results identify your unknown as an alkane, or an alkene

13. Boiling Point Determination
when you see this
Turn off heat and wait for the liquid to return into the capilliary
Note the Temperature T

14. Functional Groups
Many organic compounds also contain unique groupings with elements other than C and H
These groupings of atoms we call functional groups
Functional groups impart special chemical properties to the molecule

15. Classification Primary: carbon with –OH is bonded to one other carbon
Secondary: carbon with –OH is bonded to two other carbons
Tertiary: carbon with –OH is bonded to three other carbons
Aromatic (phenol): -OH is bonded to a benzene ring

16. Classify these:

17. IUPAC Nomenclature
Find the longest carbon chain containing the carbon with the -OH group
Drop the -e from the alkane name, add –ol
Number the chain, starting from the end closest to the -OH group
Number and name all substituents. =>

18. Name these: 2-methyl-1-propanol 2-butanol 2-methyl-2-propanol
3-bromo-3-methylcyclohexanol =>
Chapter 10

19. Naming Phenols -OH group is assumed to be on carbon 1
For common names of disubstituted phenols, use ortho- for 1,2; meta- for 1,3; and para- for 1,4
Methyl phenols are cresols.
4-methylphenol
3-chlorophenol
meta-chlorophenol
para-cresol

20. Physical Properties
Unusually high boiling points due to hydrogen bonding between molecules
Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases.

21. Acidity of Phenol In water, phenol acts as a weak acid phenol
phenoxide ion

22. Oxidation of Alcohols: Do I have a tertiary alcohol?
For Primary alcohols that dehydrogenate from the aldehyde to the carboxylic acid
tertiary alcohols do not dehydrogenate (oxidize)
Secondary alcohols only oxidize to the ketone
+ Cr3+
+ Cr3+
If chromic acid is used for H2CrO4=[O] then the product includes Cr3+ which is green

23. Oxidation with Chromate
Negative test
tertiary alcohol
Positive test primary or secondary alcohol

24. Test of a Phenol: FeCl3 test
You can test for a phenol with ferric chloride (FeCl3)
Phenol + Fe3+  [Fe3+.phenol complex]
colorless yellow purple

25. ALDEHYDES AND KETONES
The carbonyl group:
Aldehydes have at least one hydrogen attached to the carbonyl group.
Ketones have two carbons attached to the carbonyl group.

26. NAMING ALDEHYDES
Find the longest carbon chain that contains the aldehyde group.
Change ending of the root hydrocarbon name by dropping –e and adding –al.
All other branches and groups are named and located using standard IUPAC system.
Examples:
3-bromobutanal
2-ethylbutanal

27. NAMING KETONES Find the longest chain that contains C=O.
Using the root alkane name, drop the –e ending and change to –one.
Number the longest carbon chain so the C=O group has the lowest number.
Name and number other substituents as before.
Examples:
3-methyl-2-pentanone
2-methylcyclohexanone

28. ALDEHYDE AND KETONE REACTIONS
Recall the oxidation of alcohols to produce aldehydes and ketones:

29. ALDEHYDE AND KETONE REACTIONS (continued)
The difference in reactivity toward oxidation is the chief reason why aldehydes and ketones are classified in separated families.

30. ALDEHYDE AND KETONE REACTIONS
The ease with which aldehydes are oxidized allows us to test for the presence of aldehydes with Tollens’ reagent or Benedict’s reagent.
In general, ketones fail to react with these reagents.
From left to right, three test tubes containing potassium dichromate
(K2Cr2O7), acetone, and benzaldehyde.
After the addition of equal amounts of K2Cr2O7, the acetone remains unreacted, whereas the benzaldehyde is oxidized.

31. ALDEHYDE AND KETONE REACTIONS (continued)
In the presence of aldehydes, Tollens’ reagent produces a silver coating on glass.
This method is used to produce mirrors and silver ornaments.

32. ALDEHYDE AND KETONE REACTIONS (continued)
Brady’s Test for Aldehydes and Ketones
2,4-Dinitrophenylhydrazine can be used to qualitatively detect the carbonyl functionality of a ketone or aldehyde functional group. A positive test is signaled by a yellow, orange or red precipitate
RR'C=O + C6H3(NO2)2NHNH2 → C6H3(NO2)2NHNCRR' + H2O

33. alcohol, aldehyde, ketone or acid
Chromic Acid Test (1o or 2o alcohol and aldehyde only)
2,4-D Test (all ketones and aldehydes)
Tollen’s Test (aldehyde only)
Sodium Bicarbonate Test (carboxylic acid)
Boiling Point
Test Acetone, Benzaldehyde, Ethanol and your Unknown