Extraction+and+Seperation

=Introduction= Separation of different substances within a mixture is performed to do exactly that, separate the different components of a mixture. In this case, a mixture of the compounds 4-tert-butyl phenol, Benzoic acid, and 1,4-dimethoxybenzene are separated through various procedures to determine the percent yield of each substance in the completion of the experiment. Bicarbonate is used to convert carboxylic acids into ions and hydroxide ions are used to convert phenols into ions which are soluble in water. Addition of hydrochloric acid to the aqueous solutions recreates nonionic substances which are then extracted in crystal form to get the separated compounds. Thanks for including the structures. =Procedure=

Higginbotham, Carol. " Extraction and separation of a mixture ." //Central Oregon Community College//. Web. 12th Nov. 2010. http://web.cocc.edu/chigginbotham/ExtractionPrelab.html

Williamson, Kenneth L. //Macroscale and Microscale Organic Experiments//. (p.138-140). 4th. Boston, NY: Houghton Mifflin Company, 2003. Print.

Data/Analysis
Starting weight of unknown substance - 0.192g

__1,4-dimethoxybenzene (tube 1)__ Observed melting point: 37.3⁰C - 39.1⁰C Actual m.p.: 57⁰C ( Williamson, p. 138) Yield = 0.02g 0.020 grams? Did you lose a digit here? I think this is a sig figs in measurement issue. Percent Recovery = 14% formed plate crystals white, shall I assume? Color is important too.

__Benzoic acid (tube 2)__ Observed melting point: 120.8- 122.4⁰C Actual m.p.: 122⁰C ( Williamson, p. 138) Yield = 0.029g Percent Recovery = 15% formed needle crystals

__4-tert-butylphenol (tube 3)__ Observed melting point: 67.0 - 68.5⁰C Actual m.p.: 101⁰C ( Williamson, p. 139) Yield = 0.023g Percent Recovery = 12% formed plate crystals

Analysis of Data:
Due to possible contamination in tube 1 of 1,4-dimethoxybenzene, the melting point of the substance was noticeably lower than the known melting point, approximately 18⁰C lower than theoretical melting point. This same situation also appeared to have occured in the contents of tube 3 with 4-tert-butylphenol. The melting point acquired was significantly lower by about 32⁰C. The only substance recovered which had a melting point of close to theoretical was Benzoic acid, the contents of tube #2. = = =Conclusion=

The success of extracting different substances with different pka values in this experiment was good only for the strong acid. The several steps of this experiment, from pipette extraction to rinsing the solutions and crystallizing each substance, as well as keeping track of which tube contains what substance, make it difficult to be precise in the laboratory techniques of this experiment, which leads to more possible sources of error. Better percent yields and melting points could be achieved through practice of the laboratory techniques (pipette extraction and rinsing) as well as good organization at the lab bench. Again, the analysis is based on assumed starting measurements. There may have been lower or higher amounts of each substance in the starting mixture, so that the percent yields may be better than assumed or possibly worse than assumed; however, because the percent recovery of each seperate substance is fairly close in value to one another, it is possible that there were even amounts of each substance in the starting compound. Tell me as specifically as you can what you know based on the melting point data. You've drawn some reasonable conclusions, but not quite connected them back to the data.

Sources of error: It is possible hat some amount of each substance was lost in disposal of waste, as well as in extraction from one test tube to the next. Inaccuracy in pipetting technique may also be a source of error in the data. OK.

This report earned the following scores for: format (2/2) style (2/2) data (3/3) quality of result (1/1) quality of reported data (0.5/1) conclusion (1/2) error (1/1) post-lab Q (2 free points this week) for a total of 12.5/14. Well done.