Essay About Ch3Ch2Ch2Ch2Oh And Dilute Sodium Carbonate

The Preparation of 1- Bromobutane
Essay Preview: The Preparation of 1- Bromobutane
Report this essay
The Preparation of 1- Bromobutane
Introduction
Aim : To prepare 1-Bromobutane.
Background : The most common way of preparing alkyl halides, which are
very useful intermediates in syntheses, is the replacement of the OH
group of an alcohol by a halogen.
This replacement is a nucleophilic substitution reaction, and alcohols
do not undergo nucleophilic substitution reactions because hydroxide
ison is strongly basic and a poor leaving group. However, alcohols
readily undergo nucleophilic substitutions if the hydroxyl group is
first activated to produce a better leaving group, so reaction is
carried out in the presence of a strong acid. The acid protonates the
alcohol to create a suitable leaving group, water, for the SN2
reaction.
[IMAGE]
Designing…
In this experiment 1-butanol will be converted to 1-bromobutane by an
SN2 reaction.
CH3CH2CH2CH2-OH + HBr [IMAGE] CH3CH2CH2CH2-OH2 (+) Br(-) [IMAGE] CH3CH2CH2CH2-Br
+ H2O SN2
Reaction is nucleophilic substitution, and the products are impure,
and so various stages of purification are required before a sample of
reasonable purity can be obtained.
Im planning to produce 20 g of 1-Bromobutane as a result of this
experiment.
Amount of Butan-1-ol needed:
74 : 70 : 137 : 18 ß Relative Molecular Mass.
Proportion is 74 to 137 at 100% yield, so 137 g of Bromobutane will be
formed from 74 g of Butan-1-ol.
I will produce 20 g of 1-Bromobutane, my planned yield is 70%.
So;
At 70% yield : (137/100) x 70 = 95.9 g (1 mole)
I want 20 g of C4H9Br so;
( 20 x 74 ) / 95.9 = 15.5 g , so :
Production of 1-Bromobutane will require 15.5 g of Butan-1-ol to
obtain the full amount at 70% yield.
Chemicals Needed:
* Butan-1-ol, 7.72 g. (C4H9OH)
* Sodium Bromide (powdered). (NaBr)
* Concentrated Sulphuric Acid. (H2SO4)
* Concentrated Hydrochloric Acid. (HCl)
* Dilute Sodium Carbonate. (Na2CO3)
* Calcium Chloride. (CaCl2)
* Ethanol. (C2H5OH)
* Dilute Nitric Acid. (HNO3)
* Dilute Sodium Hydroxide. (NaOH)
* 0.1 M Silver Nitrate Solution. (Approx. 2.5 g in 250 cm3)
Apparatus Needed:
* Round flask, 250 cm3
* Tap funnel to fit still head
* Ice-water bath
* Reflux condenser
* Thermometer, 0-110oC
* Still head
* Conical flask, cm3
* Test tubes
* Beaker, 250 cm3
* Filter
* Teat pipette
* Holder
Mechanism…
Mechanism for this synthesis is a nucleophilic substitution. Here are
steps:
1. Since alcohols do not undergo a nucleophilic substitution without
the presence of a strong acid, these are usually called as acid
catalised reactions, because acid acts like a catalyst.
2. Sulphuric Acid attacks to the lone pairs of electrons on the
oxygen.
3. Since Sulphuric Acid acted as a proton donor, Hydrogen joins onto
the Oxygen. Water is released (condensation). As a result Carbon
will have a positive charge, now turned into a Carbocation.
4. Sodium Bromide will dissolve in water, which will act as a
solvent. As a result, aqueous solution of NaBr will be present, in
which, NaBr will exist as Na+ and Br -. The Bromide ion, having a
negative charge, will be attracted to Carbocation, bond will form
between, and 1-Bromobutane is formed.
Risk Assessment
Many chemicals used in the experiment pose a hazard so I will need to
be very careful during the experiment. Therefore, I will be carrying
out a risk assessment using the hazcards to find out which chemicals I