Orgo Lab Report 1 - Unknown Solids and Liquid

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Results:

Unknown Macro Solid:

Unknown

Identity

Crude MP

Recrystallization Solvent

Pure

MP

Given MP

Initial mass

Final mass

% Yield

D

Benzoic Acid

122.4-123.6°C

Methanol + Water

121.6-122.6°C

122-123°C

1.0019g

0.233g

23.3%

[pic 5]

[pic 6][pic 7][pic 8][pic 9][pic 10][pic 11][pic 12][pic 13][pic 14][pic 15][pic 16][pic 17][pic 18][pic 19][pic 20][pic 21][pic 22][pic 23][pic 24][pic 25][pic 26][pic 27][pic 28][pic 29][pic 30]

[pic 31][pic 32][pic 33][pic 34][pic 35][pic 36][pic 37][pic 38][pic 39][pic 40][pic 41][pic 42][pic 43][pic 44][pic 45][pic 46][pic 47][pic 48][pic 49][pic 50][pic 51][pic 52][pic 53][pic 54][pic 55][pic 56][pic 57][pic 58][pic 59][pic 60][pic 61][pic 62][pic 63][pic 64]

[pic 65][pic 66][pic 67][pic 68][pic 69][pic 70][pic 71][pic 72][pic 73][pic 74][pic 75][pic 76]

[pic 77]

Unknown Micro Solid:

Unknown

Identity

Crude MP

Recrystallization Solvent

Pure

MP

Given MP

Initial mass

Final mass

% Yield

Q

Trans-9-(2phenylethenyl)-anthracene

130.0-131.8°C

Isopropanol

130.7-131.4°C

131-132°C

0.0993g

0.0930g

93.7%

[pic 78][pic 79][pic 80][pic 81][pic 82]

[pic 83][pic 84][pic 85][pic 86][pic 87][pic 88][pic 89][pic 90][pic 91][pic 92][pic 93][pic 94][pic 95][pic 96][pic 97][pic 98][pic 99][pic 100][pic 101][pic 102][pic 103][pic 104]

[pic 105][pic 106][pic 107][pic 108][pic 109][pic 110][pic 111][pic 112][pic 113][pic 114][pic 115][pic 116]

[pic 117]

Unknown Liquid:

Unknown

Identity

BP 1

BP 2

BP 3

Researched BP

B

Tetrahydrofuran

65°C

67-65°C

69-67°C

65°C

Conclusion: [pic 118]

When given an unknown solid at the macro or micro level, the first place to start to determine the identity of this unknown from a list is to take a melting point. By finding a melting point of an impure sample, one can find a starting base of what the unknown might be. This melting point will obviously not be the same as the melting point of a pure sample of the unknown because of the “trash” in the sample. After finding the crude melting point, looking at a list of possible solvents that may dissolve that unknown helps to separate the unknown of interest away from the additives (in this case sand). In this experiment, at the micro level, the crude melting point of unknown Q was 130.0-131.8°C, extremely close to the posted melting point for trans-9-(2-phenylethenyl)-anthracene (131-132°C). Dissolving the unknown with a “good” recrystallization solvent (or mixture of solvents) means the solution can dissolve all crystals in solution (usually when heated) and allow for crystals to reform in the same solution (usually when cooled). Having the ability to dissolve crystals in an impure sample allows for gravity filtration. Gravity filtration allows the dissolved unknown to pass through the filter paper in liquid form, leaving behind all impurities (sand). Being able to recrystallize is important so that a final mass can be found and percent yield can be calculated from the initial and final masses of your sample. In the macro portion of this experiment, the solid Benzoic Acid was able to be recrystallized with a methanol and water mixed solution (methanol to dissolve, and water to recrystallize). Benzoic acid is soluble in methanol and insoluble in water, therefore the two had to be used in unison to rid the solution of all crystals and bring them back. When the Benzoic acid, in liquid form, passed through the filter paper, all sand was left behind. The use of a Buchner funnel and vacuum allowed for the removal of excess solvent from the sample, allowing the pure benzoic acid to dry and final mass, percent yield, and pure melting points to be found.

Final mass if found by weighing the dried, purified final solid. Percent yield is found by taking the final mass, dividing by the initial mass, and multiplying by 100%. The pure melting point is found by adding the pure solid to a capillary tube and placing in the Mel-Temp apparatus and recording the range from which it begins to melt to when the sample is completely melted. The final, pure melting range should definitely be close to the predetermined melting range because there are no longer any impurities in the sample. This process is the same for the determination of the macro and micro solids in