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

2. Organic Chemistry
Of the 10 million or so compounds that are known today, about 9 million of those are carbon containing compounds
Organic Chemistry is the chemistry of these C containing compounds
Compounds made of C and H are called hydrocarbons
Organic compounds can also contain O, N, P, S and transition metals
Organic Chemistry is the chemistry at work in the cell, so encompasses biochemistry
Understanding of the cell requires an understanding of organic chemistry

3. Hydrocarbons
Compounds made up of only the elements carbon and hydrogen
R = Alkyl group contains C and H both singly bonded (alkane)

4. Functional Groups
Groups of atoms or special bonds within a hydrocarbon that are responsible for the characteristic reactions of the molecule

5. Functional Groups

6. Your turn
Your Turn
Question 1

7. Naming: The Three Basic Parts
The name for any organic molecule consists of three basic parts:
Prefixes-Parent-Suffix
Each part of the name has a purpose
Parent: many carbons in the longest chain
Suffix: tells you the main functional group
Prefixes tells you about other things attached to the main chain (if any)

8. Basic Part - Suffixes
Suffixes on the end of the name of an organic molecule tell you what major family the molecule belongs to
The suffix for an alkane is “-ane” (example ethane)
Alkene = “ene” (example ethene)
Alkyne = “yne” (example propyne)
Ether = “ether” (diethyl ether)
Carboxylic Acid = “acid” (ethanoic acid)
Alcohol = “ol” (ethanol)
Ketone = “one” (dimethylketone – aka acetone)
Aldehyde = “al” (methanal)

9. Your turn
Your Turn
Question 2

10. Basic Part – the Parent
The “parent” part of the name tells you how many carbons are in the main chain of the molecule
The main chain of the molecule is defined for alkanes as being the longest chain in the molecule
Number of C atoms
IUPAC Name
Condensed Structural formula 1
methane
CH4 2
ethane
CH3CH3 3
propane
CH3CH2CH3 4
butane
CH3CH2CH2CH3 5
pentane
CH3CH2CH2CH2CH3 6
hexane
CH3CH2CH2CH2CH2CH3 7
heptane
CH3CH2CH2CH2CH2CH2CH3 8
octane
CH3CH2CH2CH2CH2CH2CH2CH3 9
nonane
CH3CH2CH2CH2CH2CH2CH2CH2CH3 10
decane
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

11. Drawing Structures
There are many ways to draw or write a chemical formula/structure for a given organic molecule
Consider the hydrocarbon decane
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

12. Your turn
Your Turn
Questions 3,4

13. Parent and suffix…
The parent is named based on the number of carbons
1 carbon = “meth”
So a one-carbon alkane is called methane
CH4

14. Parent and suffix… CH3CH3 2 carbons = “eth”
So a two carbon alkane is called ethane.
CH3CH3

15. Parent and suffix… CH3CH2CH3 3 carbons = “prop”
So a three carbon alkane is called propane.
CH3CH2CH3

16. Basic Part – Prefixes
Prefixes are the bits and pieces that are attached to the main chain (parent) of the molecule
An example of a prefix might be a halide attached to the main chain as in:

17. Prefixes – the Halides
The family called alkyl halides does not have a suffix.
Halides are always named as prefixes.
Fluorine is called “fluoro”
Chlorine is called “chloro”
Bromine is called “bromo”
Iodine is called “iodo”

18. Putting together a name…
The rules for IUPAC nomenclature include:
Step 1: Find the main chain
Step 2: Number the main chain
Step 3: Identify all prefixes and their position numbers
Step 4: Write the full name: Prefixes-Parent-Suffix

19. Now let’s take a look:
Follow the rules… Name this molecule…

20. Find the main chain…
The longest chain in this molecule has seven carbons… and only a halide (which is always named as a prefix).
This is heptane.

21. Number the chain…
This molecule is symmetrical. It doesn’t matter if we go left to right or right to left… that bromine is attached to carbon #4

22. Final Answer?
If you put the prefix first, then parent and suffix, what do you get?
“Bromo hept ane” includes all of the pieces, except for indicating where the bromine is attached...
4-bromoheptane is the complete name.

23. What would you do different..?
How would you name this one?
Number this asymmetric molecule by beginning your numbering from whichever end is closest to the first substituent (aka: branch, prefix).

24. So in this case…
You would number from left to right, so the bromine winds up on position #3.
If you numbered from the other end, the bromine would be on #5.
Always aim for the lowest possible number on the first substituent!

25. Final Answer?
3-bromoheptane

26. Alkyl Groups
Alkyl groups are named similarly to alkanes, based on the number of carbons in the fragment
A fragment of methane, CH4, would be CH3-
This fragment is called “methyl” where “meth” stands for one carbon and “yl” stands for fragment (alkyl group).

27. Methyl Group The molecule shown here has a 7-carbon main chain.
Notice that it has a branch attached to carbon #4. This branch has a single carbon – a methyl group.
4-methylheptane is the name of this compound.

28. Ethyl Groups
A two-carbon alkane is called ethane, CH3CH3. The corresponding two-carbon fragment is always CH3CH2-, which is called “ethyl”.
4-ethylheptane is the name for this one.

29. Propyl Groups
There are two possible three-carbon alkyl groups to form from propane, CH3CH2CH3.
The straight chain version: CH3CH2CH2- which is called “propyl” or “n-propyl” (where n stands for “normal” or straight-chained)
2-propyl-butane?
3-ethyl-pentane?

30. Name first 8 structures in last question
Your turn
Your Turn
Name first 8 structures in last question

31. 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 ending with the suffix ene

32. 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)

33. 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

34. Name the last 4 structures in the last question
Your turn
Your Turn
Name the last 4 structures in the last question

35. Aromatics Aromatics contain This is called benzene
This is called toluene (methyl benzene)
What is this one called?
Ethyl-benzene

36. Alkane Reactions: Oxidation
Alkanes are unreactive because they are so stable
All alkanes combust (burn in air) to make carbon dioxide and water
Very exothermic because O-H and C=O bonds are much more stable than C-C and C-H bonds
If there is not enough oxygen one gets incomplete oxidation of the alkane

37. Reaction with O2 (combustion)
Combustion can be used to indicate the nature of the hydrocarbon
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

38. Your turn
Your Turn
Do Questions 1&2

39. Alkane Reactions: Halogenation
Replacement of one or more H with a Halogen
F, Cl, Br, I
Reaction requires the halogen to first break apart into free radicals which can happen when heated or exposed to UV light
If there is light present then a series of chain reactions can occur, creating all sorts of products but the reaction is slow
Slow step needs light
Chain propagation
Chain termination

40. Your turn
Your Turn
Do Question 3

41. Addition Reactions of Alkenes
C=C double bonds are generally less stable than C-C
X-Y
H-F, H-Cl, H-Br, H-I
H2, F2, Cl2, Br2,I2
H-OH

42. + Alkene / HCl Thermochemistry H-Cl RCH=CH2
The relative instability of C=C
= 249
= 263
single double
three singles
H-Cl
RCH=CH2
H-RCH-CH2-Cl or Cl-RCH-CH2-H? +
H-Cl
H2C=CH2
H-CH2-CH2-Cl +
The reaction is favorable by 14 kcal/mol
= 57kJ/mol 99
103 83 81
What about selectivity?
Is addition of HX across an unsymmetric alkene regioselective or not?
146

43. Reactions: Alkenes Reaction with Br2,Cl2 etc
Br- adds from other side entering a C-Br σ* antibonding molecular orbital of a bromonium ion (more room)
In cyclic compounds you get the trans isomer
Reaction is faster than with alkanes

44. 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

45. Your turn
Your Turn
Do Questions 4-7

46. Reactions: Alkenes
Reaction with Potassium Permanganate Baeyer test (create diols)
Alkane or aromatic (negative test)
Alkene (positive test)
In acid
Purple
Light Pink
Ethane-1,2-diol
In base

47. Your turn
Your Turn
Do Questions 4-7

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

49. Name these: 2-methyl-1-propanol 2-butanol 2-methyl-2-propanol
3-bromo-3-methylcyclohexanol

50. Naming Phenols
When an –OH is attached to a benzene ring we call it a phenol
-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

51. Alcohols: Classification
Alcohols have an –OH functional group attached to a C
The reactivity of the alcohol depends on how many C are attached to the C-OH
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

52. Classify these alcohols as 1o, 2o, 3o or a phenol and name them:
Primary Alcohol
1o, 2-methyl-1-propanol
Tertiary Alcohol
3o, t-butanol (or 2-methyl-2-propanol)
Pheno
2o, phenol
Secondary Alcohol
2o, 2-butanol

53. Oxidation of Alcohols: Do I have a tertiary alcohol?
Primary and Secondary alcohols can be oxidized (dehydrogenation)
Primary alcohols are oxidized to the aldehyde and then the carboxylic acid
Secondary alcohols only oxidize to the ketone
tertiary alcohols do not oxidize
+ Cr3+
+ Cr3+
If chromic acid is used for H2CrO4=[O] then the product includes Cr3+ which is green

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

55. Test of a Phenol: FeCl3 test
Phenols do not oxidize
You can test for a phenol with ferric chloride (FeCl3)
Phenol + Fe3+  [Fe3+.phenol complex]
colorless yellow purple

56. 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.

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

58. NAMING KETONES Find the longest chain that contains C=O.
Using the root alkane name, drop the –ane ending and change to –anone.
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

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

60. ALDEHYDE AND KETONE REACTIONS (continued)
The difference in reactivity toward oxidation with an oxidization agent (O) is the chief reason why aldehydes and ketones are classified in separated families.

61. ALDEHYDE AND KETONE REACTIONS
The ease with which aldehydes are oxidized allows us to test for the presence of aldehydes with oxidizing agents
In general, ketones fail to react with these reagents
Here is an example using Chromic Acid.
K2Cr2O7 acetone benzaldehyde.
No reaction Oxidation
Ox agent ketone aldehyde

62. 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.

63. Brady’s Test for Aldehydes and Ketones
2,4-Dinitrophenylhydrazine (2,4 D) can be used to detect the carbonyl (C=O) of a ketone or aldehyde
2,4 DNP + aldehyde/ketone  yellow, orange or red precipitate

64. alcohol, aldehyde, ketone or acid?
Chromic Acid Test (1o or 2o alcohol and aldehyde only)
2,4-DNP Test (all ketones and aldehydes)
Tollen’s Test (aldehyde only)
Sodium Bicarbonate Test (carboxylic acid)
Boiling Point