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Chemistry

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Nov 24, 2024

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Purpose: The aim of this experiment is to, using 4 reactions (bromination, oxidation, reverse bromination, and treatment with oxylic acid), to convert cholesterol to a 4—cholesten-3-one molecule. Theory: A liquid heated in an open container’s vapor pressure increases until it reaches the vapor pressure of the atmosphere. The normal boiling point is defined as the temperature at which a liquids vapor pressure reaches the standard value of one atmosphere (also descried as 101.325 KPa. It is more efficient to calculate the boiling point of a molecule using the boiling point depression as boiling points vary depending on the atmospheric pressure available. The boiling point depression formula is B.P.D. = (760 mmHg-obs.atm.pressure in mmHg) x (0.037oC/mmHg). According to Raoult’s law the partial vapor pressure of a compound in a solution is equal to its vapor pressure times its mole fraction in a solution. Temperature and composition of a liquid also influences vapor pressure. As temperature varies the vapor pressure of a solution also varies with the composition that the liquid has, so, the boiling point also changes as composition changes. The boiling point of such mixture is reached when P°ANA + P°BNB= P atmosphere. If in the solution of a mixture the A component has lower boiling point, the vapor from the mixture will contain more than the liquid of component A at any temperature. Once the mixture is distilled the quantity of A in the vapor phase will be greater than the quantity that remains in the flask. Some mixture of miscible liquids form azeotropes. An azeotrope mixture is a mixture where two components are distilled without change in composition or boiling point regardless of their boiling points differing by 25 o C or even more. There are two types of Azeotropic mixtures: minimum boiling point (where the azeotropic has lower boiling point than that of pure component) and maximum boiling point where the azeotropic has lower boiling point than that of pure component). An azeotrope cannot be separated by distillation process completely, Also its composition depends on pressure (as the pressure changes the composition of azeotropic also changes). Sometimes the mixture of two components contain vapor pressure that are in EQM or close enough to make the process of distillation ineffective, so, fraction distillation can be used to effect separation of the two components. A vapor-liquid composition has the ability to shows that as component A becomes richer in vapor A, the remaining component B becomes richer in B. Therefore, as the process of distillation proceeds the boiling point of the remaining liquid (in flask) increases (B). so, we can conclude that the liquid flowing back has a more condensed vapor and lower boiling point compared to vapor rises up the column.

Procedure: Part 1:  Add 3g of cholesterol to 30 mL of ether and dissolve it (heat solution).  Add 15 mL of Bromide-anhydrous sodium acetate solution.  Then let the solution to cool down in an ice bath.  Once the solution is cool collect the product by suctioning and rinse with 25 mL of acetic acid solution. Part 2:  Take a 250 mL beaker and suspend the moist dibromide in 40 mL of glacier acetic acid and allow to heat up to 45 0 C.  Measure out 40 mL of sodium dichromate and pour it to the acetic anhydrite solution and keep on heating (only between 55 0 C- 60 0 C).  Using a stirring rod, stir the solution for about 5 minutes.  Let the solution set aside in an ice bath for 10 minutes.  Now add 15 mL of water and make sure the temperature does not exceed 15 0 C.  Filter by suctioning.  Rinse with 10 mL of methanol (and repeat the above 2 steps again). Part 3:  Pour all the dibromo cholestanone into a beaker (125 mL) and mix 40 mL of diethyl ether and 0.5 mL of glacial acetic acid into it.  Transfer the mixed solution to ice bath and mix 2g of zinc dust to it.  Stir to mix for 10 minutes in the ice bath and 15 minutes out of the bath (Once out of the bath make sure to add 1 drop pyridine to the solution).  Filter the mixture by gravity and wash the precipitate with ether.  Move the solution to 125 mL of separatory funnel.  Then wash it with three 20 mL portions of water, with 25 mL of 5% sodium bicarbonate (once).  Test the solution with litmus paper and ensure the solution is neutral.  Then prepare to extract the ethereal solution with 30 mL of saturated sodium chloride solution.  Filter the ether layer through a filter with anhydrous sodium sulphate into 100 mL beaker.  Evaporate to 25mL.  Add 10mL of methanol and evaporate to 20 mL.  Crystalize the solution in an ice bath.  Then collect by suction. Part 4:

 Heat up 1g of 5-cholesten-3-one, 0.1g of anhydrous, and 8 mL of 95% ethanol until dissolved.  Recrystalize, and re-filter by gravity. Hazards: o Sodium acetate Exposure controls/personal protection: goggles and gloves. toxicology information: can cause irritation to eyes and skin. If ingested or inhaled it can be toxic to liver, kidney, and CNS. first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move into a fresh air area and if ingested wash with water. o Sodium dichromate Exposure controls/personal protection: goggles and gloves. toxicology information: can cause irritation to eyes and skin. If ingested or inhaled it can be toxic to lungs liver and kidneys. first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move into a fresh air area and if ingested wash with water. o ceric ammonium nitrate Exposure controls/personal protection: goggles and gloves. toxicology information: can cause irritation to eyes and skin. Toxic to kidney, liver, heart, CNS and thyroid if ingested or inhaled. first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move into a fresh air area. o Zinc dust Exposure controls/personal protection: goggles and protective gloves. irritation toxicology information: can cause irritation to eyes and skin. first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. o Pyridine Exposure controls/personal protection: goggles and gloves required.

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toxicology information: ca be toxic to blood, liver, kidneys, central nervous system, eyes and skin. first aid measures in case of emergency: In case of contact with skin and eyes rinse off with water immediately for 15 minutes. o Ethanol Exposure controls/personal protection: goggles and gloves required. toxicology information: toxic to blood, liver, kidneys, central nervous system, eyes and skin. first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move into a fresh air area. o Ether Exposure controls/personal protection: goggles and protective gloves. irritation toxicology information: can cause irritation to eyes and skin. It can also be hazardous if ingested and inhaled. It is toxic to lungs, and mucosa membrane. first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move into a fresh air area. o Acetic acid Exposure controls/personal protection: goggles and gloves. toxicology information: can cause irritation to eyes and skin. If ingested or inhaled it can be toxic to liver, kidneys and CNS and heart. first aid measures in case of emergency: If irritation is too much call a physician. if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move to a fresh air. o Methnol Exposure controls/personal protection: goggles and gloves. toxicology information: very hazardous. it is able to cause irritation to skin. If ingested or inhaled, it can cause damage to eyes, lungs, liver, kidneys, and CNS. first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move into a fresh air. Sodium bicarbonate Exposure controls/personal protection: hazardous in case of skin contact and eye contact so goggles and gloves must be worn.

toxicology information: got the ability to cause potential damage to eyes and skin , nose and throat, coughing, chest discomfort and gastrointestinal disturbance. first aid measures in case of emergency : in case of a hazardous contact wash for 15 minutes straight. o Sodium sulfate Exposure controls/personal protection: goggles and gloves required. toxicology information: toxic to blood and kidneys. Can also cause eyes and skin (irritation). first aid measures in case of emergency: if in contact with skin and eyes rinse off with water immediately for 15 minutes. If inhaled move into a fresh air area. o Oxylic acid Exposure controls/personal protection: gloves and goggles. toxicology information: vey hazardous to kidneys, heart, mucosa membrane, eyes and brain. It can also cause eyes and skin (irritation). first aid measures in case of emergency: in case of a hazardous contact wash for 15 minutes immediately. PART 2 (4) 1. The mixture to be separated in the experiment concept video is composed of two compounds selected from this group of solvents: OH Ethanol n-Hexane CH 3 OH Methanol H 2 O Water Write out all possible combinations of solvents. Assemble all relevant analytical data: boiling point, formation of azeotropes, refractive indices, miscibility with water.

2. Consider a solution of a mixture of compounds A and B. Use Raoult’s Law to find the partial pressure at atmospheric conditions (101.3 kPa) of compound B with a mole fraction of 0.4 if compound A has a partial pressure of 62.8 kPa and a mole fraction of 0.6. Show all calculations.

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