Synthesis Of 1-Bromobutane

November 15, 2007

Synthesis of 1-Bromobutane

Introduction:

The purpose of this experiment is to synthesize 1-bromobutane from 1-butanol and sodium bromide. In order for this reaction to reach completion there are four major operations that need to be performed. The four major operations include refluxing, simple distillation, separation, and drying.

To begin, in order for the compounds to react they will be dissolved in water and sulfuric acid will be added. The addition of sulfuric acid will then generate hydrobromic acid, an important product in the reaction mixture. The hydrobromic acid will react with the 1-butanol when heat is added to the flask during refluxing. Refluxing is the heating of a flask to boiling and then allowing the vapors to condense and run back into the reaction flask. Refluxing is a good way of keeping a reaction at a constant temperature.

After refluxing is complete the reaction is allowed to distill by way of simple distillation. The simple distillation process is used to help remove and purify a particular substance, in this case the 1-bromobutane, from other components in the reaction flask. However, since the boiling point of 1-bromobutane is 101oC and the boiling point of water is 100oC it would be expected that there would be a large amount of water that will distill out of the flask along with the 1-bromobutane. Other remaining reactants such as a small amount of alcohol and/or acid may also be distilled out along with the water or 1-bromobutane.

Since there is such a high probability of other components in the distillate, separation processes will need to be carried out. Sulfuric acid is first added to the 1-bromobutane layer to remove any leftover starting material and after the 1-bromobutane layer is isolated sodium hydroxide solution is added to remove any remaining acid. Drying using anhydrous calcium chloride pellets is then used to remove any remaining water in the solution and then the simple distillation process is performed again on the dried 1-bromobutane.

It would be hypothesized that the amount of recovered 1-bromobutane will be relatively low since there are many techniques involved, which allow for many places for error and product loss. Also, the theoretical yield for the experiment is 1.5g, which is relatively low.

After the recovered 1-bromobutane is weighed, infrared spectroscopy will be performed. It would be hypothesized that the 1-bromobutane spectrum would produce peaks at the characteristic alkane and halogen peaks; an alkane C-H bond at less than 300cm-1 and a halogen compound peak at less than 650cm-1.

Chemical Chart:

Structure Formula Molecular Weight Melting Point Boiling Point Density Vapor Pressure Water Solubility

1-butanol

C4H10O 74.12 g -89.5oC 117.6o 0.81 g/cm3 4 kpa Soluble 6.32 g/100mL

1-bromo butane

C4H9Br 137.02 g -112oC 101oC 1.276 g/cm3 0.06 g/100mL Insoluble

Water

H2O 18.02 g 0oC 100oC .995 g/cm3 3.2 kpa at 25oC >= 10g/100mL at 19oC

Sodium Bromide

NaBr 102.89 g 755oC 1390oC

Sulfuric Acid

H2SO4 98.07 g 3oC 280oC 1.84 g/cm3 Soluble; Miscible; Reactive

1-butene

C4H8 56.11 g -185.3 oC -6.1oC Insoluble

Di-n-butyl ether

C8H18O 130.23 g -95oC 141oC .764 g/cm3 4.8 kpa Insoluble <0.1 g/100mL at 22.5oC

Acetone

C3H6O 58.08 g -94.3oC 56.2oC .7857 g/cm3 181 kpa Miscible

Ethanol

C2H6O 46.07 g -114.1 oC 78.3oC .789 g/cm3 7.87 kpa at 25oC Miscible >= 10g/100mL at 23oC

Sodium Hydroxide

NaOH 39.997 g 318oC 1390oC 1.11 g/cm3 0 kpa 50 g/100mL Highly Soluble

Calcium Chloride

CaCl2 110.986 g 782oC 1600oC

P-xylene

C8H10 106.167 g 13.3oC 138.3 oC .861 g/cm3 8.6 kpa Insoluble

Safety Precautions:

While performing this experiment a lab coat, gloves, and goggles were worn at all times to protect skin, clothes, and eyes. Caution was taken in handling sulfuric acid since it is a highly reactive substance and can cause serious burns. Care was taken with acetone, ethanol, butyl ether, 1-butanol, and vapors of 1-butene because they are all flammable. Care was also taken while handling glassware. All filtrates and chemicals were disposed of in the proper waste containers.

Reaction Mechanism:

NaBr, H2SO4

CH3CH2CH2CH2OH CH3CH2CH2CH2Br + NaHSO4 + H2O

(1-Butanol) (1-Bromobutane)

Flowchart:

-Reflux for 30 minutes

-Perform Simple Distillation

-Simple Distillation

-Infrared Spectroscopy

Observations:

* After adding sulfuric acid to the mixture of NaBr, 1-butanol, and water there was a brief yellow stream that appeared