Organic synthesis

a. Alcohols and alkenes are versatile chemicals that are often involved in many organic synthetic reaction schemes.

Butan-1-ol can be converted directly into 1-bromobutane.

State the reagents and conditions required for this conversion.

b. Heating butan-1-ol with concentrated sulfuric acid causes the loss of a small molecule.

State the type of reaction involved and name the resulting alkene.

a. The reagents and conditions required for this conversion are NaBr in H₂SO₄ solution under heat with reflux.

Remarks: There are various synthetic routes for preparing organic molecules. The answer will be acceptable as long as it’s suitable, for example, slowly adding PBr₃

b. The type of this reaction is called elimination or dehydration

The resulting alkene is but-1-ene

Describe one simple test-tube reaction that allows you to distinguish between compounds G and H shown in

One simple test-tube reaction that allows you to distinguish between compounds G and H is using acidified potassium dichromate(VI) solution because compound G with secondary alcohol can be oxidised to a ketone along with colour change from orange to green, while there is no change in compound H because ketone will not reaction with acidified potassium dichromate(VI) solution

a. A reaction pathway is shown in

State the reagents and conditions required for the conversion of compounds

b. Name compound C shown in figure above in part (a)

c.

i. Compound B reacts with cold dilute potassium manganate(VII) to form compound D. Draw the structure of compound D

ii. Compound B also reacts with hot concentrated potassium manganate(VII) to form compounds E and F. Draw the structure of compounds E and F

a. But-2-ene can be converted into butan-2-ol by two different synthetic routes. One route can be carried out as a one-step process whilst the other requires two steps.

State reagents and provide an equation, using structural formulae, for the one-step process

b. Draw a reaction scheme, including reagents and conditions for the two step process

a. The reagents and an equation, using structural formulae, for the one-step process 

Reagents: steam in acid catalyst

Equation:

 `CH_3CHCHCH_3 + H_2O -> CH_3CHOHCH_2CH_3`

b. A reaction scheme, including reagents and conditions for the two step process

But-2-ene -> 2-bromobutane -> butan-2-ol

Step 1: HBr solution

Step 2: aqueous alkaline hydroxide

A series of reactions based on butan-1-ol is shown

Identify every suitable reagent and conditions as well as structure in figure above

Some reactions of compound A are shown in

a. Draw the skeletal structures of compounds B, C and D

b. Compound A reacts with iodine and sodium hydroxide ions to give two products. Draw the skeletal structures of these two products

The reaction scheme shows three steps to synthesise 2-hydroxy-2-methylpropanenitrile from propene.

Suggest the reagents and conditions required for theses reactions including compounds

Lactic acid occurs naturally, for example in sour milk

What is a property of lactic acid?

A. It decolourises aqueous bromine rapidly

B. It is insoluble in water

C. It reduces Fehling’s reagent

D. It reacts with sodium carbonate

The answer is D

 It will create a salt with CO₂ and H₂O

A is incorrect because bromine water is decolorised when we have alkene compound

B is incorrect because because it has carboxylic acid group and alcohol which both have polar properties

C is incorrect because only aldehyde reacts with Fehling’s reagent to form carboxylic acid

Which reagent can be used to convert `CH_3CH_2CO_2CH_3`into `CH_3CH_2CO_2CH_2Cl`?

A. Chlorine in bright sunlight at 100 °C

B. Concentrated hydrochloric acid at 100 °C

C. Phosphorus pentachloride at room temperature

D. Sulphur dichloride oxide (thionyl chloride, SOCl₂) at 50 °C

The answer is A

This reaction will be occurred via free-radical substitution in which a halogen atom will replace one H atom to create a new molecule.

B, C and D are incorrect because these compounds are used in the nucleophilic substitution for the conversion of alcohols.

A compound C has the following properties:

• liquid at room temperature
• soluble in water
• reacts with aqueous sodium hydroxide

What could C be?

A. Propene

B. Propanol

C. Propanoic acid

D. Propyl propanoate

The answer is C

A is incorrect because it is a gas and insoluble in water as well as not reacts with aqueous sodium hydroxide

B is incorrect because it is a liquid and soluble in water but not react with aqueous sodium hydroxide due to a weak base

D is incorrect because it is not soluble in water