Chemistry Organic synthesis topic 16

16.1 -16.2

What are the main components and their functions of a reflux? (6)

1. Verticle condensor that allows liquid vapour to renter the reaction mixture

2. Open space on the top of the condensor attached with a clamp stand to prevent explosion

3. A pear shaped flask that allow every drop of the solution to be heated up evenly- avoid sudden bumping

4. Anti-bumping granules to prevent glasswear from vibrating violently- boil smoothly

5. Heating mantle that provides even heat

6. Rubber tubing to connect apparatus

What happens inside a reflux?

1. Reaction mixture is heated up and evaporated up the condensor

2. Vapours condenses into liquid before it reaches the top and escape

3. The liquid vapour drops back into the pear shaped flask and continue to boil

What are the 3 main benefits of using a reflux?

1. It allows reaction mixture to be heated for a long period

2. It prevents the loss of volatile substances

3. It allows reactions to occur faster

Compare the two types of distilation.

1. Simple distilation is used for seperating a soluble solid and liquid

2. Fractional distilation is used for seperating a mixture of miscible liquids with different boiling points

They are both useful for:

1. purifying a liquid- removes impurities

2. Seperate liquids with different boiling points

What are the main components and their functions in a distilator? (11)

1. Horizontal condensor that prevents liquid vapours from rentering the reaction mixture

2. Round-bottomed flask (attached with a fractional column for fractional distilation)

3. Thermometer- moniter the temperature to ensure only the wanted liquid turns into vapours (identify the substance)

4. Clamp and a stand for holding the flask

5. Still head that attaches the condensor with the flask

6. Receiver - leads liquid to the conical flask

7. Conical flask- collect product

8. Second clamp for the receiver and conical flask

9. Heating source- bunsen burner in blue flame

10. Tripod and wire gauze

11. Screw- cap adaptor that connects thermometer and flask

What happens inside a distilator?

1. Mixture is heated up and the liquid with the lowest boiling point evaporates first and reach the thermometer

2. The vapour flows into the condensor through the still head and cools down

3. When it turns into liquid , the distlate is collected in the conical flask through a receiver

What are the main components and their functions of a seperating funnel? (4)

1. Stopper- stop or allow liquid to flow through the tap

2. Clamp and stand

3. Tap- stop or allow liquid to flow to the beaker

4. beaker- collect liquid

How do we use a seperating funnel?

1. Ensure the tap is closed

2. Pour immiscible mixture in the container

3. Put on the stopper and invert to mix

4. Let the layers to settle and add water to identify aqueous layer

5. Place a beaker underneath and remove the stopper and open the tap until one of layer leave and collected by the beaker

What is the purpose of redistilation?

To further purify an original liquid as the original liquid may contain impurities, side products and unreacted reactants.

How do we identify a pure and impure liquid.

Pure substances have a sharper boiling point and a narrower boiling range.

Impurities alter the boiling point of the original substance because the intermolecular forces are distrupted

What are the two examples of drying agents?

MgSO₄ and CaCl₂

What are drying agents and what do they do?

Drying agents are anhydrous inorganic salt that remove water from organic liquids.

Solid hydrated salt formed can be filtered off

Identify this functional group: R-CH(=O)

Aldehyde

Identify this functional group: R- C(=O)OH

Carboxylic acid

Identify this functional group: R- C(=O)Cl

Acyl chloride

Identify this functional group: R- COO-R

Ester

Identify this functional group: R- C(=O) -R

Ketone

Identify this functional group: -NH2

Amine

Identify this functional group: -CN

Nitrile

List and describe the 4 kinds of mechanisms.

1. Electrophilic addition is when a pi (double) bond breaks to form 2 new sigma bonds. Electron pair in the double bond attacks an electrophile to make unsaturated hydrocarbons saturated.

2. Elimination- when a 2 functional groups leave the main molecule, forming a double bond, turning a saturated hydrocarbon into an unsaturated one

3. Free radical substitution- where a halogen replaces a hydrogen atom in an alkane and are split into 3 stages including initiation, propagation and termination

4. Nucleophilic substitution- Where a nucleophile (electron donar) attacks a carbon atom (electrophile intermediate) and replace the old, leaving group. There could be 1 or 2 steps mechanism for different classification of the organic molecule.

What is the mechanism and process called when alkene turns into dihaloalkanes (include conditions needed)?

Electrophillic addition

Halogenation

Halogen at room temp

What is the mechanism called when alkene turns into haloalkanes (include conditions needed)?

Electrophilic addition

hydrogen halide

What is the process called when alkene turns into polymers ?

Additional polymerisation

What is the mechanism called when haloalkanes turns into alkenes (include conditions needed)?

Elimination

NaOH in ethanol under reflux

What is the mechanism and process called when alkene turns into alkanes (include conditions needed)?

Electrophilic addition

Hydrogenation

H₂ and nickel

What is the process called when alkane turns into alkenes (include conditions needed)?

Cracking

High heat/ catalyst

What is the mechanism called when alkane turns into haloalkanes (include conditions needed)?

Free radical substitution

UV light and halogens/ halide radicals

What is the mechanism and process called when alkene turns into alcohol (include conditions needed)?

Electrophilic addition

Hydration

Steam and H₃PO₄ or H₂SO₄ phosphoric acid or sulfuric acid

What is the mechanism and process called when alcohol turn into alkene (include conditions needed)?

Elimination

Dehydration

H₂SO₄ + heat

What is the mechanism called when alcohol turns into haloalkanes (include conditions needed)?

nucelophilic substitution

NaBr or NaX and H₂SO₄ under reflux

What is the mechanism and process called when haloalkanes turns into alcohol (include conditions needed)?

Hydrolysis

nucelophilic substitution

warm OH^- or H₂O under reflux

What is the process called when alcohol turns into aldehyde (include conditions needed)?

Partial oxidation

Primary alcohols under distilation + oxidising agents like acidified potassium dichromate K₂Cr₂O₇

What is the process called when alcohol turns into carboxylic acid (include conditions needed)?

Full oxidation

Primary alcohols and under reflux + oxidising agents like acidified potassium dichromate K₂Cr₂O₇

What is the process called when alcohol turns into ketone (include conditions needed)?

Full oxidation

Secondary alcohols under reflux + oxidising agents like acidified potassium dichromate K₂Cr₂O₇

Name the typical reactions/ mechanism for alkanes. (1)

Free radical substitution

Name the typical reactions/ mechanism for alkenes. (2)

1. Electrophilic addition

2. Addition polymerisation

Name the typical reactions/ mechanism for alcohol. (3)

1. Nucleophilic substitution

2. Dehydration/ elimination

3. Oxidation

Name the typical reactions/ mechanism for haloalkanes. (1)

1. Nucleophilic substitution

Name the typical reactions/ mechanism for aldehyde. (1)

Oxidation (further)

Name the typical reactions/ mechanism for carboxylic acids. (2)

1. Neutralization

2. Esterification (with alcohol)

How can we find a target molecule using two stage synthesis when the starting molecule doesn’t react directly? (3)

1. Identify both functional groups in both starting and target molecule

2. Identify intermediate that links reactions

3. State reagents and conditions for each step.