Preparation of Bromotriphenylmethane

Preparation of Bromotriphenylmethane

Abstract The structure of a major component of star anise oil was derived by analyzing its IR spectroscopy melting point of after oxidation and purification. From the evidence obtained, it was concluded that the exact structured should be p-methoxybenzoic acid. Introduction The purpose of this experiment is to determine the structure of the major component of star anise oil. It is already known that this component has a molecular formula C10H12O. This molecular formula equates to an IHD of 5. It is evident, by calculating the IHD, that this compound contains a benzene ring. By heating anisene with hydroiodic acid the following reaction occurs: [rxn 1] The resultant of a phenol indicates that anisene is, in fact, an aryl methyl ether with the formula C9H9OCH3. Since all these facts have been established about the structure of anisene, what is to be determined from this experiment is the structure of the unsaturated side chain and its location. In order to do this, anisene will first be oxidized with KMNO4 so as to then identify the oxidation product and establish the positioning of the side chain. The reaction is as follows: Finally purification of the structure of the unknown oxidized component, its structure shall be determined by obtaining the melting point and by means of IR spectroscopy of the original substance. Experimental The experiment was carried out following the procedure described in Experiment 24 of the assigned lab book (Lehman 188-195) with some deviation: When it was time to use the condenser the first time around, the tubes for the water to circulate were not attached, causing the solvent to evaporate. Consequently, more solvent had to be added and the experiment continued normally. Calculations The weight of the total final product is equal to the weight of the watch glass and the final product minus the weight of the watch glass. Wt of Final product = (wt of watch glass and product)-(wt of watch glass) =51.10-50.88= 0.22 grams Calculation of Percent Yield: The molecular weight of each is compound (triphenylmethane and triphenylbromide) is measured by looking at the periodic table and adding each of the existing elements' molecular weights corresponding to each compound. The theoretical yield is calculated by multiplying the amount of the triphenylmethane used by the molecular weight of triphenylbromide and then dividing by the molecular weight of the triphenylmethane. The percent yield is calculated by dividing the actual yield by the Theoretical yield. Molecular Weight of triphenylmethane=3*(6*12+ 5*1) +12 + 1=244g/molMolecular Weight of triphenylbromide=3*(6*12+ 5*1) +12 + 80=323g/mol Theoretical yield=(wt of triphenylmethane used)(MW of triphenylbromide)/(MW of triphenylmethane)==0.22grams(323grams/mol)/(244grams/mol)= 0.291grams of triphenylbromide Percent yield=(Actual yield/Theoretical yield)*100=(0.22grams/0.291grams)*100=76% yield Results The melting point of triphenylmethylbromide is 154 degrees celcius.The product created started melting at 151 degrees celcius and was finished melting at 154 degrees celcius indicating the substance obtained was a relatively pure substance containing triphenylmethylbromide. The percent yield of 76% indicates that there was only a small amount of sample lost. Discussion The low percentage yield may be associated with a scale malfunction. The fact that this particular scale registered 0.00g the first time the product was weighed is indicative of this. In addition, from the time the same was weighed the first time to the time that it was weighed again, a sample was taken for the melting point. A significant amount of the sample may have been accidentally spilled during this process. Another cause for the low percentage yield may be due to the fact that during the recrystallization process, the 10 mL beaker recommend in the procedure may have been too small for the amount of solvent that need too be added (causing some of the mixture to possibly spill.) Finally, with such low percentage yield, it is impossible to conclude any information about the product. On the other hand, the melting point range of 181-183 degrees celcius is strongly indicative that the final product is p-methoxybenzoic acid. With this information, it may now be possible to consider studying supporting evidence of this in the IR spectrum of the final product. From the IR spectrum it is concluded that the structure contains C-H sp3 and sp2 hybridized carbon bonds. In addition, the fingerprint region--although mostly illegible--indicates the presence of an aromatic ring. Exercises 1. (a) Show how Gomberg's dimer, ;whose