Yanzon Post Lab 4.docx

YANZON, Janea Michaela B. Locker No. 40B Experiment #4: Identification of an Unknown through Quantitative Analysis 26/03/19 Data and Results

H2SO4

X X

5% HCl

X X

5% NaHCO3

toluene cyclohexene t-butanol ethanol

5% NaOH

Sample

water

Table 1. Solubility Test Results of the Unknown and Functional Group Standards.

X

X

X Base: amine Acid: Carboxylic acid Neutral, Ester, Alcohol, Amide, Ether, Aldehyde, Ketone Neutral, Alcohol, Ester, Amide, Ether, Aldehide, Ketone

acetone ethyl acetate benzaldehyde unknown

Indications

X

X

X

X X

X

Acid: Carboxylic acid

Table 2. Functional Group Test Results of the Unknown and Functional Group Standards. A. Ignition and Bayer Tests Observations/Indications Sample Ignition Test Bayer Test Yellow flame with toluene - (purple) soot/Unsaturated Yellow flame without cyclohexene + (brown) soot/Saturated Yellow flame with t-butanol - (purple) soot/Unsaturated Yellow flame without ethanol - (purple) soot/Saturated Yellow flame without acetone - (purple) soot/Saturated Yellow flame without ethyl acetate - (purple) soot/Saturated Yellow flame with benzaldehyde + (brown) soot/Unsaturated Yellow flame without unknown - (purple) soot/Saturated

Sample toluene cyclohexene t-butanol Ethanol acetone ethyl acetate Benzaldehyde unknown

Sample toluene cyclohexene t-butanol Ethanol Acetone ethyl acetate benzaldehyde Unknown

Sample toluene cyclohexene t-butanol ethanol acetone ethyl acetate benzaldehyde unknown

B. Lucas and Chromic Acid Tests Observations/Indications Lucas Test Chromic Acid Test - (orange) - (had a 2nd layer due to - (yellowish dark green due to solubility issues) hydrated benzene) - (clear) - (orange) - (clear) + (dark blue green) - (clear) - (reddish orange) - (clear) Partial reaction (dark brown) - (had a 2nd layer due to + (dark brown with precipitate) solubility issues) + (white/milky, 2nd layer formed) - reddish orange color C. Hydroxamic Acid and Iodoform Tests Observations/Indications Hydroxamic Acid Test Iodoform Test - (didn’t turn red violet, more iron) - (yellow orange) - (white yellow) - (yellow) + (yellowish precipitate) - (bright yellow) + + (turned red violet) - (yellow) - (light green) - (clear) D. 2,4-DNPH and Tollen’s Tests Observations/Indications 2,4-DNPH Test Tollen’s Test - (orange) - (slightly yellow) - (insoluble orange) - (dirty yellow) - (orange) - (yellow) - (orange) - (yellow) + (orange precipitate) - (yellow) - (orange) - (yellow) + (orange precipitate) + (silver mirror) - (no precipitate formed, orange) - (black)

E. Iron (III) Chloride and Alcohol Silver Nitrate Tests Sample toluene cyclohexene t-butanol ethanol acetone ethyl acetate benzaldehyde unknown

Observations/Indications Iron (III) Chloride Alcohol Silver Nitrate + (clean layer) + (clean layer) - (gold) - (yellow) - (clear) - (brown) - (yellow) - (clear)

Physical Properties of Unknown #21 Appearance: clear Odor: pungent Discussion For this experiment, qualitative organic analysis tests were performed on different samples and one unknown. These tests are used for identifying the different functional groups present in a certain compound through properties such as solubility and reactivity with different reagents as formation of precipitates and color changes). In the first day of this experiment, the seven standard compounds (toluene, cyclohexene, t-butanol, acetone, ethyl acetate, benzaldehyde and ethanol) were analyzed to see the positive and negative results and other possible observations for these tests. After obtaining these results as a group, the unknown sample was analyzed individually in day 2 of the experiment in order for its functional groups to be identified. Through a process of elimination from a list of possible compounds, the identity of the unknown is determined. The tests are categorized into two: the solubility tests and the functional group tests. The only test the unknown sample was positive in was the Lucas Test which was indicated by the formation of a 2nd layer. This indicates the presence of a secondary alcohol (AtQ<1>). Cross-referencing all the tests, the unknown sample is most probably propanal (AtQ<2>). The limitations of these qualitative tests is that it would be difficult to know the true structure of the compound because these tests can only detect certain functional groups. Specific structures cannot be seen and the only way to narrow down the possible chemicals is to give a set of standards something to compare with or a set of chemicals with which one of them is surely the unknown sample (AtQ<3>). Modern analytical techniques like infrared spectroscopy would give the same information as qualitative tests. They also provide information on the presence of certain functional groups. It would also be more precise in finding out what kind of functional group is present since it deals with specific wavelengths and measurements. Qualitative tests are also subject to human error and also, subjectivity in observing indicators such as formation of precipitates and reactions happening (AtQ<4>).

Sample Calculations

none References Most CF. Experimental Organic Chemistry. USA: Wiley & Sons; 1988. Palleros DR. Experimental Organic Chemistry. USA: Wiley & Sons; 2000. Organic Chemistry Teachers’ Association (OCTA). A Laboratory Manual of Basic Chemistry. Philippines: Graphic Arts; 1973.