Qualitative Synthesis Lab Report

Introduction
The purpose of this experiment was to find the identity of the unknown compound #12. This was done both qualitatively and quantitatively. The qualitative observations were used to determine the functional group that was in the unknown, the quantitative results were used to determine the molar mass through Duma’s method. The types of compounds that were used in testing were all functional groups, Aldehyde, Ketone, Alcohol and, Ester. Functional groups are a portion of a molecule that give the molecules its properties, they are the centers of chemical reactivity. The structures of the functional groups used in testing are displayed in Figure 1.0. Figure 1.0 Structure of Functional Groups to Distinguish from Within the
For each of these tests, except the ester test, one sample of the unknown and another for the known was made, and then the 2 test tubes were compared. For aldehydes Tollen’s reagent was used, 1 mL was placed into both test tube along with one have 2 drops of the unknown #12 and another with 2 drops of the aldehyde. For Ketones a reagent called phenylhydrazine (C6H5NHNH2) was used, 1 mL of it was added to both test tubes with one test tube having 2 drops of the unknown and the other the 2 drops of ketone. For the alcohols 3 test tubes were used, 2 mL of Lucas reagent was added to each test tube with one having 5 drops of a primary alcohol, another with secondary alcohol and the last one with unknown #12. Next they were put into boiling water and observed until the secondary alcohol turned cloudy. The final qualitative test was for the Esters, both the unknown and the known’s fragrance were compared. Next, was the quantitative test. An Erlenmeyer flask with aluminum foil and a rubber band mass was measured and then filled with 4 mL of unknown #12. The flask was then covered and had a hole poked through the foil. Next, it was placed into boiling water. After the liquid was fully evaporated it was taken out, wiped dry and, allowed to cool. Then the mass was measured. Then the lab station was cleaned and the waste properly disposed of.
This method assumes that the liquid neither dissociates or associates in going from liquid to vapour, thus the molecular mass of the liquid would be the same of the vapour [1]. With Dumas’ method the resulting molar mass was 73.44 g/mol. This does make sense because in the results it was determined that the functional group was an ester and there are two esters that are very close in molar mass, methyl acetate and ethyl formate. The methyl acetate and the ethyl formate both have a molar mass of 74.08 g/mol [5][6]. The last step is to distinguish between the two. Both methyl acetate and ethyl formate are described as having a “fruity odour”, relatively close boiling points and the same colourless appearance [5][6]. However, there is one source that says that methyl acetate has a “characteristically pleasant smell reminiscent of some glues and nail polish removers” [7]. For the ester test in the lab, the unknown and the ester did smell a lot like nail polish remover. One method of discovering the specific ester one had is to taste it. Each ether has a different taste, for methyl acetate it’s described as a “fleeting fruity taste” [5], and for ethyl formate it’s described as having a slightly bitter taste [6]. The main potential source of error is when using the Dumas’ method one must poke a hole into the tin foil. This is effective in the case that it allows one to use the