1. Chapter 10.2 & Chapter 20.1 Organic Reactions
ALCOHOLS

2. Alcohols Ex: Ethanol (alcohol in alcoholic beverages)
3 types of general RXNs
Combustion (much like alkanes/alkenes)
Form CO2 and H2O (if complete)
C and CO (if incomplete)
More carbons = higher energy output
Oxidation reactions
e- are removed and e- density of a molecule is reduced
Often involves removal of H atoms from organic molecule
Esterification reactions
A type of Condensation RXN where water is produced

3. Alcohols- Oxidation
Combustion is considered complete oxidation of alcohols
These reactions are actually partial oxidation of alcohols
Primary alcohols  aldehyde  carboxylic acid
Secondary alcohols  ketone
Tertiary alcohols  No reaction
3 types of alcohols

4. 1º alcohols (ex. Ethanol) can be oxidized twice.
First oxidation yields aldehyde R—CH=O
Second oxidation yields carboxylic acid R—COOH
Requires: Oxidizing agent
Acidified sol’n of potassium dichromate (K2Cr2O7) or +[O]
K2Cr2O7 is orange in color
After oxidizes something (been reduced itself) turns green

5. 1º Alcohols- Oxidation In the 1st oxidation: distillation
In the 2nd oxidation: reflux
Oxidation is the reason why wine (alcohol) turns to vinegar (carboxylic acid) over time exposed to air

6. 1º Alcohols- Oxidation nifty fact
Basis for a type of simple breathalyzer test (detect ethanol in the breath)
The subject breathes into a device containing orange colored crystals of acidified potassium dichromate
If ethanol is present in the breath, it will be oxidized by the acidified potassium dichromate, turning the crystals to a green color
This color change is detected by a photocell, and the level of change is proportional to the amount of alcohol in the breath

7. 1º Alcohols- Oxidation Distillation
Oxidation of 1º alcohols can occur in two steps
So, possible to isolate 2 cmpds in right conditions
If want aldehyde:
Distillation
Used to allow the aldehyde to be removed before the reaction goes further

8. 1º Alcohols- Oxidation Distillation
Mixture of the 1º alcohol (ex. ethanol) and the oxidizing agent (acidified potassium dichromate) is heated in a flask
As the aldehyde (ethanal) is formed, the heat causes it to boil
Aldehyde vapors travel to condenser
The cooler temp converts back to a liquid and they are removed

9. 1º Alcohols- Oxidation Reflux
If want carboxylic acid:
Aldehyde must be oxidized further before it is removed from the reaction chamber
This is accomplished by using reflux
Aldehyde vapor is not allowed to escape from the condenser
Instead, it drips back into the flask where it contacts the heated oxidizing agent and is converted into the carboxylic acid

10. 2º Alcohols- Oxidation Secondary alcohols (ex. propan-2-ol)
Only undergo one oxidation
Acidified potassium dichromate is a suitable oxidizing agent in this reaction as well

11. 3º Alcohols- Oxidation
Tertiary alcohols are not easily oxidized because this would require breaking the carbon skeleton of the molecule (too much E required)

12. Alcohols- Oxidation For primary alcohols
 aldehyde (distillation)
 carboxylic acid (reflux)
For secondary alcohols  ketone
For tertiary alcohols  no reaction
All RXNs require at least
Acidified potassium dichromate and heat

13. Alcohols- Esterification
Condensation RXN
RXN where 2 molecules combine to form a larger one
This results in a loss of a small molecule
Esterification: a type of condensation RXN
Carboxylic acid + alcohol ester + water

14. Alcohols- Esterification
Requires: concentrated H2SO4
The alcohol will lose an -H and the carboxylic acid will lose an -OH to form water
R-C=O from carboxylic acid and O-R from alcohol will bond to form the R-COO-R’

15. Alcohols- Esterification
Boiling point of ester < alcohol or carboxylic acid
Alcohols and carboxylic acids H-bond
Therefore, ester can be separated from RXN via distillation
Also, tend to be insoluble so come out of solution (layer on top of reaction mixture)