Resolution of the Enantiomers of Ibuprofen Chm 255

Resolution of the Enantiomers of Ibuprofen

Due date: Monday, November 10, 2014

Date submitted: Monday, November 10, 2014

• Purpose: analyze the resolution of the medicinally active (S)-(+)-ibuprofen enantiomer from a racemic mixture by using crystallization.

• Structures/Reaction:

|(S)-1-phenylethylamine |racemic ibuprofen |

|Sodium Hydroxide |Hydrogen Chloride |

• Calculations

1°/[(.079g/25mL)x1dm] = 316.5

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1°/61.7° x 100% = 1.62%

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50+(294.6%/2) = 197.3

100-197.3 = -97.3

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% S Recovered = .079g/.133g x 100 = 59%

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% (S,S) salt yield = .133g/.322g x 100 = 41.3%

• Results

| |Mass of sample(g) |volume (mL) |cell length(dm) |[α] (blank) |

|S-ibuprofen |+61.7° |1.62% | |-97.3 |

|R-ibuprofen |-52.2° |294.6% |197.3 | |

% (S,S) salt yield = . 41.3% % R Recovered = 2.17%

% S Recovered = 59%

Dissucion Questions:

1. The percent yield was quite low, being less than 50%. What may have caused the low percent yield is fault in the experiement, and specifically fault in the first part of the lab. There could have been error in keeping the temperature constant, or the stir bar not actually stirring the solution to obtain maximum results. Also, at one point of the reflux, after adding the (S) -1-phenylethylamine, we forgot to turn back on the water for refux, therefore losing solution to evaporation .

2. Our calculated specific rotation values are...