Surname Lab Report


Theexperiment’s purpose was to isolate the amount of cholesteroldibromide. Several methods were used to create cholesterol dibromide.Some of the methods were vacuum filtration that was used to collectsolid crystal from the solution. The second method used wascrystallization that led to formation n of crystals that weremeasured and tabulated to determine the amount of cholesteroldibromide obtained. The procedure that was applied was that 100mg ofmethyl t-butyl ether was measured, and bromine was added. Thecrystals began to form crystals that were then isolated by use ofvacuum filtration. The addition of acetic acid was to remove methylt-butyl ether (Klein, 113).

Cholesterol dibromide


Br2, C5H12O, Et2O


Weightof cholesterol dibromide recovered (mg) 75 mg

Theoreticalyield of cholesterol dibromide 153 mg

Percentage(%) recovered of cholesterol dibromide 49%

Meltingpoint of the cholesterol dibromide (0C) 102 – 108 0C


Toget the theoretical amount of the cholesterol dibromide obtained

Molecularweight of the Cholesterol dibromide = 546.47g/mole which isequivalent to 546.47 mg/mmole

Molecularweight of Cholesterol is 386.7 g/mole which is equivalent to 386.7mg/ mmole

Amountof cholesterol used is 100 mg

Thereforethe amount of cholesterol needed to be produced is:

108mg of cholesterol * {546.47 mg (MW cholesterol bromide)/ 386.7 mg (MWof cholesterol)}

=153mg of cholesterol bromide

Thepercentage of the produced cholesterol about the theoretical valuewill therefore be:

(75mg/153 mg) * 100%s



Inthis process initially the cholesterol will react with the brominewhen the solutions are mixed forming cholesterol dibromide. It is anaddition reaction since cholesterol molecule is unsaturated that isto say that it has a double bond in its structure. The reaction isalso called halogenation since it involves the addition of a halogenthat, in this case, is bromine in carbon to carbon double bond ofcholesterol. So the bromine and cholesterol undergo additionalhalogenation reaction to form cholesterol dibromide. The reaction isalso electrophilic. It is because all substances with double bondsundergo electrophilic reaction where, in this case, cholesterolhaving a carbon – carbon double bond will undergo electrophilicreaction with bromine. In electrophilic reaction, one molecule oratom is looking for electrons which, in this case, cholesterol havinga double bond to break the bond it is in need of the electron that isin this case contributed by the bromine atoms thus making them reactto form the product. Excess bromine was added in the solution ofcholesterol to ensure that all the cholesterol are reacted in theprocess to obtain the maximum amount of the end products i.e.cholesterol dibromide.

Asthe reaction preceded the cholesterol dibromide formed the smallcrystal in the solution since it is insoluble n the solution ofmethyl t – butyl ether. The acetic acid in vacuum filtration helpsin washing the crystals with unreacted bromine and unreacted bromine,methyl t-butyl ether and acetic acid were filtered away while smallcrystals of cholesterol dibromide were collected and dried. Theweight and melting point was then determined (Klein, 118).

Inthis reaction, only 49% of the cholesterol dibromide is formed incontrary to the 100% of the expected amount in the reaction. Also,may be attributed to different factors as the reactions proceeds asdiscussed later in the sources of errors.

Sourcesof Errors

Someof the errors occurred were: When bromine was transferred from theflask to the vacuum filters some of the bromine volumes remained inthese flasks basically on the wall a factor that led to obtaining ofthe wrong value thus creating an error. Secondly, during the additionof the bromine solution to the cholesterol solution maybe more of thebromine was used the required amount leading to the obtaining of theinaccurate values thus. Thirdly, the presence of the impurities inthe cholesterol or the bromine solution can cause a large effect onthe level of the reaction of this solution thus making the endproduct register negative results than expected. Furthermore, theimpurities will alter the melting point of the solution by decreasingit rather than it being normal which in return leads to the lowermelting point of the cholesterol dibromide thus the real value.Lastly, the reaction time may be too little to ensure that all thebromine solution reacts completely with the cholesterol to form thecholesterol dibromide thus leading to inaccurate results (Klein,123).


Toconclude, the purpose of this experiment was to separate thecholesterol dibromide that was in the mixture which resulted from thereaction of the cholesterol from the cholesterol solution and brominefrom bromine solution when they were mixed. According to theexperiment, only 49% of the cholesterol was able to be collected outof the 100% theoretically. The melting point of the cholesteroldibromide collected was only between 102 -108 0C contrary to thenormal melting point of 110 0C. Furthermore only 48 mg out of 141 mgthe literature value was collected. All this was attributed todifferent errors made here and there in the course of doing anexperiment. Therefore, it’s clear that if the error were to becorrected the reactions and the value to be obtained would beaccurate and precise (Klein, 125).


Klein,D. (2012). Organicchemistry.Hoboken, N.J.: John Wiley.