Hayley Williams

In this experiment, un unknown solid was identified by using a Thomas Hoover Apparatus to determine the mixture melting point. The melting point (mp) range for Unknown #3 was 109.5C-112.7C. The mp range was compared to the known mp for a set of solids provided in a data table. The closest matches to Unknown #3 (acetanilide, 113-115C; fluorene, 114-116C) were mixed with the unknown substance to find mixture mp. The results concluded that the unknown was acetanilide because the melting point measured was within the literature mp range.

In the Thin Layer Chromatography (TLC) experiment, food dyes, analgestic tablets, and three different solvents were used to identify and determine polarity of known and unknown compounds. In the food dye experiment, the developing solvent used was composed of 1-butanol, ethyl acetate, ethanol, water and glacial acetic acid. In the two analgestic experiments, the two solvents used were ethyl acetate and acetic acid, and ethyl acetate and hexanes. Once the TLC plates developed, they were viewed by both the naked eye, and under ultra violet light. R f values were calculated using the equation, R f =distance from baseline traveled by solute/distance from baseline traveled by solvent. The higher the Rf value, the less polar the compound was. Rf values did not exceed 1.0.

In the Crystallization experiment, glass wool, a Hirsch funnel, and a hot plate were key pieces of equipment used to purify a naphthalene compound through the process of recrystallization. Impure naphthalene crystals were heated and dissolved in a methanol solute, then cooled and filtered through the Hirsch funnel using vacuum filtration. The pure recrystallized naphthalene crystals were weighed to find the percent error. The purity of the recrystallized naphthalene was proven by using a Thomas Hoover Apparatus to find the observed melting point (79.5C) that could then be compared to the, nearly identical, literature melting point (80.26C). Of the initial 1.014g of impure naphthalene collected, 0.764g of pure naphthalene were recovered after the recrystallization, demonstrating a 75.3% recovery. Purpose/Theory

The purpose of this experiment was to identify two unknowns by separating a mixture using fractional distillation. The process of fractional distillation was used to separate two components of a mixture based on the differences in boiling points of the two. The mixture was heated and the unknowns separated, lower boiling point first, through the process of evaporation and condensation into marked test tubes. Once the unknowns were separated, a refractive index was measured using a refractometer to further confirm the identity of the two compounds. The unknown mixture used in this experiment was unknown #6, which was a mixture of methanol (lower BP) and 2-methyl-1-propanol (higher BP). Methanol has a boiling point of 64.7C and a refractive index of 1.3292, while unknown A had an average boiling point of 70.1C and a refractive index of 1.3341. Unknown A's BP and RI came the closest to methanol's BP and RI, confirming that it was methanol. 2-methyl-1-propanol has a boiling point of 108C and a refractive index of 1.3960, while unknown B had an average boiling point of 106.1C. These similar values confirmed the identity of unknown B as 2-methyl-1-propanol. Boiling points and refractive indices were used to match the unknowns with a known compound.

In the Extraction experiment, liquid-liquid extraction was used to separate and purify naphthalene and benzoic acid from a mixture of the two through a separatory funnel. This process works by dissolving the naphthalene/benzoic acid mixture into two different solvents, one aqueous and one organic (ether) solution. Naphthalene was combined with the organic solvent, tert-butyl methyl ether (TBME) and the benzoic acid was combined with the aqueous solvent, sodium hydroxide (NaOH). These two solutions did not mix due to differences in polarity, making it possible to separate the two through the funnel. Once the extraction was finished, the recrystallization process was used to remove the pure compounds from their respective solvents and the percent recoveries of naphthalene (49.0%) and benzoic acid (71.4%) were calculated. To confirm the purity of the recrystallized naphthalene and benzoic acid, a thin layer chromatography (TLC) experiment was performed comparing the two pure compounds to the original mixture of the two. The R f values were then calculated for the pure naphthalene (0.224), benzoic acid (0.830), and the two parts of the original mixture (naphthalene: 0.269, benzoic acid: 0.810). The similarities of the R f values concluded that the " pure " naphthalene and benzoic acid were, indeed, pure. Melting points would have further-supported the purity of the isolated substances, but they were not measured in this experiment due to time constraints.

The objective of this experiment was to produce triphenylmethyl methyl ether (TPMME) via an S n 1 substitution reaction. The " reflux " method was applied to run the reaction. Methanol was mixed with triphenylmethyl chloride (TPMCl) and then added to a round-bottom flask to be heated and boiled for fifteen minutes. During the fifteen minutes of boiling, the vapors travelled through a simple distillation apparatus, leaving TPMME in the flask to be crystallized. The TPMME was recrystallized using vacuum filtration and tested for purity using a TLC test. The theoretical yield of the TPMME (2.000g) was used to calculate the % yield (50.45%) based on the mass of the recovered TPMME (1.009g). The results of the TLC tests between the product, starting material and a sample of the two combined, concluded that the TPMME was pure. This was determined because the R f value of the product (0.568) was very similar to the R f value of the pure TPMME (0.523) that was separated from the combined sample. Even though the % yield was on the lower side, the sample produced showed to be very pure.

The intention of this lab was to learn how to isolate caffeine from tea leaves using the method of extraction. Six teabags were steeped for 2 minutes before sodium carbonate was added. In a separatory funnel, the cooled tea/sodium carbonate mixture was added, followed by 3 rounds of 20mL of ethyl acetate. The mixture separated into an aqueous layer (tea and water) and an organic layer (caffeine and ethyl acetate). The aqueous layer was discarded and the organic layer was drained into a clean flask. The caffeine was recrystallized using a RotoVap. Once isolated and recrystallized, the purity of the caffeine was to be determined via melting points and thin layer chromatography. The end-goal of the experiment was to determine the percent recovery of caffeine extracted from the tea bag with a 2% mass assumption and the % recovery by mass. The extracted caffeine was compared to pure caffeine in a TLC test and the Rf values were compared to assess the purity of the extracted sample. The calculated Rf value for the pure caffeine was 0.625 and the Rf value for the extracted caffeine was 0.596. The similar Rf values concluded that the extracted caffeine was mostly pure. The % recovery based on the 2% mass assumption was 59.6%. The % recovered based on the mass of the teabags as a whole was 1.17%, which means 59.6% of the 2% mass of caffeine in the teabags was recovered. Melting points were not measured due to time constraints.

The main objective of this experiment was to perform a microscale preparation of benzoic acid via the Grignard reaction. Once the benzoic acid was prepared, it was recrystallized and the purity of the product was assessed by measuring the melting point. Lastly, the % yield was measured to determine how much product was created. To a reaction tube containing 52mg of magnesium, 0.5mL of dry, anhydrous ether was added along with 1mL of bromobenzene through a syringe. A reaction occurred and the phenyl-magnesium bromide (product) was poured over dry ice (CO 2). The ice melted and the ether evaporated, leaving a glassy substance behind (magnesium bromide salt of benzoic acid). The addition of hydrochloric acid dissolved the remaining metal and pure benzoic acid was crystallized via vacuum filtration and purity was assessed by measuring the melting point. When the experiment was completed, the % yield was measured (5.29%), showing some inefficiencies. The melting point was then measured and since the product MP range(87-89ºC) was so much lower than the literature MP (122ºC), the product was not pure.

The objectives of this experiment were to study the optical rotation of enantiomers using polarimetry and to understand how concentration, cell length, observed rotation (α obs), and specific rotation [α] are related. Measurements of specific rotation and enantiomeric excess were calculated and chirality centers were identified. Another objective was to learn and identify the relationship between stereoisomers. The enantiomers used in this experiment were: (R)-(-)-Carvone, (S)-(+)-Carvone, (S)-(-)-Limonene, (R)-(+)-Limonene, unknown substance A, and sucrose solution B. The unknown was identified ((S)-(-)-Limonene) by comparing the observed rotations. Once all rotation values were calculated, % error was found for R-(-)-carvone (4.26%) and R-(+)-limonene (28.27%) in part A, % ee was found for (S)-(+)-Carvone (69.5%) and (S)-(-)-Limonene (56.4%) in part B, % difference for [α] of unknown A/(S)-(-)-Limonene and known [α] (4.26%) was found in part C, and the concentration of the sucrose solution (0.221 g/cm 3) was calculated.