The Preparation of 1-bromobutane

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The Preparation of 1-bromobutane

 The aim of this assignment is to produce 1-bromobutane in the

 laboratory and write a report on the preparation.

 To do this, I will need to follow the following steps:

 - Carry out the reaction by reflux

 - Separate the 1-bromobutane from the reaction mixture

 - Purify the 1-bromobutane

 - Test for it's purity

Background Information

 ----------------------

 One way of preparing 1-bromobutane is to start with btan-1-ol and

 replace the -OH group on it with a - Br group by means of a

 substitution reaction. The reaction can be represented by the

 equation:

 CH3CH2CH2CHOHHBr → CH3CH2CH2CH2Br + H2O

 This is a nucleophilic substitution reaction, which comes about by the

 reaction between butan-1-ol and Br- ions. The reaction is done in the

 presence of a strong acid and the first step involves bonding between

 H+ ions and the O atom on the alcohol:

 This gives the C atom to which the O is attached a partial negative

 charge. It is now more readily attached by Br- ions forming

 Bromobutane.

 The overall equation for the reaction is: CH3CH2CH2OH +® Br-CH3CH2CH2CH2Br

 + H2O.

 Structural Isomers

 Isomers are molecules that have the same molecular formula but have a

 different arrangement of the atoms in space. That excludes any

 different arrangements, which are simply due to the molecule rotating

 as a whole or rotating about particular bonds.

 Structural isomers are molecules, which have the same molecular

 formula but have different connectivity's.

 Types of structural Isomerism

 Chain Isomerism: These isomers arise because of the possibility of

 branching in carbon chains. For example, there are two isomers of

 butane, C4H10. In one of them, the carbon atoms lie in a "straight

 chain" whereas in the other, the chain is branched.

 Position Isomerism: In position isomerism, the basic carbon skeleton

 remains unchanged, but important groups are moved around on that

 skeleton.

 For example, there are two structural isomers with the formula C3H7Br.

 In one of them the Bromine atom is on the end of the chain, whereas in

 the other hand it's attached in the middle.

 Another similar example occurs in alcohols such as C4H9OH

 These are the only two possibilities provided you keep to a

 four-carbon chain.

 Functional group isomerism

 In this variety of structural isomerism, the isomers contain different

 functional groups i.e. they belong to different families of compounds

 (different homologous series).

 For example a molecular formula C3H6O could be either propanal (an

 aldehyde) or propane (a ketone)

 Possible Isomers of 1-bromobutane

 1)C4H9Br

 H H H H

 Â½ ½ ½ ½

 H-C- C- C- C-H

 Â½ ½ ½ ½

 H H Br H

 2-bromobutane

 2) H H H H

 Â½ ½ ½ ½

 H-C-C-C-C-Br

 Â½ ½ ½ ½

 H H H H

 1-bromobutane

 3) H

 Â½

 H H - C-H H

 Â½ ½ ½

 H-C - C - C -Br

 Â½ ½ ½

 H H H

 2-methyl 1-bromobutane

 4) CH3

 Â½

 CH3 - C - CH3

 Â½

 Br

 2-bromo 2-methyl propane

 Uses of 1-bromobutane

 1. It is used in the preparation of alcohols e.g. hydrolysis of

 1-bromobutane produces 1-butan-1-ol

 2. William synthesis: it is used in the preparation of ether. When a

 halogeno alkane is refluxed with an alcoholic solution of sodium

 alkoxide, ether is produced.

 E.g. CH3CH2CH2CH2Br + CH3COO-Na+

 CH3CH2CH2CH2-O-CH2CH3 + NaBr

 3) It is used in the formation of esters.

 CH3CH2CH2CH2Br + CH3COO-Na+

 Sodium ethanoate

 Butyl ethanoate

 ( ester)

 Equipment: To carry out the experiment, I will require the following

 apparatus and chemicals:

 1. 10 cm3 measuring cylinder 15. Long teat pipette

 2. Butan-1-ol (7.5cm3) 16. Conc. Hydrochloric acid (10cm3)

 3. Access to balance 17. Sodium hydrogencarbonate solution, 5%

 4. 50cm3 pear-shaped flask 18. Anhydrous sodium sulphate

 5. Sodium Bromide (10g) 19. Test tubes (2)

 6. Tap funnel and stopper 20. Small funnel with cotton wool plug

 7. Distillation head 21. Glass rod

 8. Clamp and stand 22. Small beaker

 9. 250cm3 beaker (for water bath) 23. 0-110°C thermometer and holder

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 10. Conc. Sulphuric acid (10cm3) 24. Specimen tube

 11. Anti-bumping granules

 12. Reflux condenser

 13. Guard tube containing soda lime

 14. Small Bunsen or electric heating mantle

 Risk Assessment

 Chemical

 Hazard

 Corrective plan

 Butan-1-ol

 Harmful/flammable

 - avoid contact with skin

 - wear lab coat

 - if spilled clean up area with cold water

 - keep far away from Bunsen flame

 - wear eye protection.

 Concentrated hydrochloric acid ...

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