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UM - CHEM 205 - Class Notes - Week 1

UM - CHEM 205 - Class Notes - Week 1


School: University of Miami
Department: Chemistry
Course: Organic Chemistry Lab 1
Professor: Lab ta
Term: Fall 2014
Tags: CHM205, Organic Chemistry Laboratory, orgo lab 1, UM, and Miami
Cost: 25
Name: CHM205/Organic Chemistry Lab 1 (UM)
Description: FULL LAB REPORTS and POSTLAB questions for the entire course. FINALS NOTES cumulation document also included - from Lab textbook, class notes, exam review summary.
Uploaded: 09/29/2014
84 Pages 181 Views 17 Unlocks

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Full Lab Reports

Organic Chemistry 1: CHM 205

  • Pipets and Melting Points
  • Recrystalization
  • Extraction
  • Thin Layer Chromatography
  • Column Chromatography
  • Making Polymers
  • Simple and Fractional Distillation
  • Steam Distillation
  • Resolution of Enantiomers

Organic Chemistry 2: CHM 206

  • SN1 and SN2 Reactions
  • The Diels-Alder Reaction
  • The E1 Reaction: Synth of Cyclohexene
  • Nitration of Methyl Benzoate: A Macroscale Synthesis
  • The Fischer Esterification: Synth of an Ester
  • ID of an Unknown Ester: Transesterification and bp
  • OFF, an Insect Repellent
  • The Grignard Reaction: Synth of Benzoic Acid
  • Aldol Condensation
  • Oxidative Cleavage: Synth of Adipic Acid
  • Infrared Spectroscopy: An Exercise
  • Nuclear Magnetic Resonance Spectroscopy Exercise
  • Nuclear Magnetic Resonance Spectroscopy: A Second Visit

Post Lab Questions

Define melting point range based on the two values that are used to describe a compound’s melting point.

The melting point range is the range of temperatures at which a solid will become a liquid. The first temperature indicates where the intermolecular forces begin to break and the last temperature indicates the point at which all of the forces have broken.

What is the proper heating rate used to determine a compound's melting point range? What do you think would happen if you exceeded this heating rate?

The proper rate of heating is 1-2°C/minute. If you exceed this rate it would be difficult to accurately determine the melting point range because melting would happen so quickly.

Suppose you are trying to determine the melting point of a compound, and the following happens: Describe what happened in each case. How would you either report or correct this?

a. The compound turns from white to brown before melting If the compound turns from white to brown before it melts, this probably means it is decomposing into a different product first which is indicated by the color change. b. The compound slowly disappears from the capillary tube before melting The compound often shrinks (or appears to shrink) before melting. It should melt normally after this.

Find literature melting points for the following pairs of compounds

a. Ferrocene: about 170-174°C and Acetylferrocene: 81-83°C b. Adipic acid: 151-153°C and Citric acid: 153-155°C

Adipic acid and citric acid have very similar melting points. Given two unknown samples, one being citric acid and the other adipic acid, how could you determine which was which (without using spectroscopy)? Explain in detail.

You could determine the melting temperatures of the two samples individual using the MelTemp. The sample with the lower melting point range would be adipic acid. Or, you could take a sample of what you know to be adipic acid and mix it with one of the unknowns. Then, determine the melting point of the mixture. If the melting point range is not lowered or broadened, that means the unknown used in this mixture was adipic acid. The same could be done for citric acid.

The solubility of an unknown compound X in ethanol is found to be 0.21 g per 10mL at 0°C and 1.4 g per 10mL at 78°C. What is the minimum amount of ethanol needed to recrytallize a 2.0 g sample of compound X? After recrystallization of the 2.0 g sample,how much of the compound X will remain dissolved in the cold solvent(ie. How much of compound X is not recovered after the recrystallization)?

Why is it important to use only the minimal amount of hot solvent needed to achieve a recytallization? What would be the effect of using too much solvent while dissolving a solid for recrystallization?

What do you think would happen to your recrytallization solution if you did not use a preheated filter during the 'hot' gravity filtration step?

Benzyl alcohol has a b.p of 205°C. It has a solubility characteristics that would seem to make it a good choice for use as a recrytallization solvent for flurorenol (mp 152-155°C), but in fact benzyl alcohol is a poor choice of solvent for this recrystallization. Why do you think this is?

Explain how each of the following contaminants is removed during the recrystallization process:
  • a. Sand (inorganic contaminant)
  • b. Colored organic contaminants
  • c. A very soluble contaminant

Your TA may have told you to use acetone to clean your glassware after you finished your experiment. Acetone is a very popular solvent for cleaning glassware. Given the properties of acetone listed in MtC, why do you think this is? Do you think acetone would make a good recrystallization solvent? Why or why not? From a safety standpoint, what do you suppose would be a major concern when using acetone?

Truamatic acid has a distribution coefficient of 5.8 between MtBE and water. If 75 mg of traumatic acid is added to a centrifuge tube containing 3 mL of water and 2 mL of MtBE, how much traumatic acid would be in each layer after through mixing?

Given a solution of 10 mg of traumatic acid dissolved in 100 mL of water and using the partition coefficient given for traumatic acid in Qu1, show that extracting the 100 mL of aqueous solution with two 10 mL portions of MtBE would recover more of the traumatic acid from the aqueous solution than one extraction using 20 mL of MtBE.

Suppose that just before adding a drying agent to an organic solent that was used to extract an aqueous solution, you notice that there are still tiny water droplets in the organic layer. Can you proceed with adding drying agent? What should you do?

Devise a general extraction scheme for separating the following pairsa). an organic base mixed with an organic neutral compound (B+N)b). an organic acid (HA) and a phenol (ArOH)

When 2 immiscible solvents are mixed, 2 layers form. Liquid-liquid extractions commonly use organic solvents that are less dense than aqueous solvents that are less dense than aqueous solutions, and therefore form the top layer. An important exception to this rule is chlorinated solvents, which are often more dense than aqueous solutions, and form the bottom layer. Suppose you were unsure which layer was which during your extraction. What simple method do you think you could use to determine which of the 2 layers was the aqueous?

Potassium carbonate is an excellent drying agent, but it should not be used with some classes of organic compounds. Would it be a better choice to use in drying an ether solution containing and acid (RCOOH) or a base (RNH2)? Why?

MCAT Practice Test Questions

Soil contains organic matter called humus. Humus is classified into humic and nonhumic materials. Humic materials are operationally divided into 3 main fractions: humic acid, fulvic acid and humin. Fraction B is thus more likely:

A mixture of sand, benzoic acid, and naphthalene in ether is best separated by

Suppose an extraction with methylene chloride (d=1.4g/mL) is performed, with the desired compound initially in brime (d =1 g/mL). In a separatory funnel, which layer will be the organic layer?

o-Hydroxyacetophenone has a melting point of 4-6?C. p-Hydroxyacetophenone has a melting point of 109-111?C. Explain the basis for the sizable difference in melting points of these two compounds

In running TLC under the following conditions, you get results that are less than ideal. Consider the situation in each case and suggest a correction
  • You run TLC on a mixture of 2 unknown halogenated alkenes, but you see only one spot with a Rf of 0.15. The solvent used was ethyl acetate
  • You run TLC on a mixture of a thiol and an amine, and again you get only one spot with a Rf of 0.15. The solvent was a mixture of petroleum ether and dichloromethane
  • When you put your TLC plate in the developing chamber, the solvent in the chamber covered the spots on the TLC plate baseline

You run a TLC plate spotted with 3 compounds: naphthalene, o-toluric acid and fluorenol. Predict the relative Rf values

For each of the following pairs, predit which compound will have a larger Rf value if both are run on a SiO2 TLC plate in 10% acetone/hexane: 4-decanone or 4-decanol; xylene or benzoic acid; cycloheptane or cycloheptanone.

Arrange the following solvents in order of increasing polarity: ethyle acetate – dichloromethane – n-propanol – ethanol – toluene – heptane

Name 3 important things to keep in mind while spotting TLC plate.

Why does ferrocene elute form the column first? Why was the solvent hanged in the middle of the column procedure?

Ferrocene eluted fomr the column first, but it ended up as the higher of the two spots during TLC analysis. Explain?

Why is it important to limit the sand bath temperature to around 60 °C when evaporating solvent from your collected fractions?

You run a column to separate a mixture of 3 compounds: naphthalene, o-turic acid and fluorenol. The column is run with a solvent system based on hexane, but which becomes more polar with the addition of more and more dichloromethane over time. Predict the elution order

Suppose you are given 150 mg of an unknown mixture that contains 3 compounds, and you are told to us CC, using alumina as a stationary phase. How would you decide what solvent or solvent system to use?

The compounds used in Exp 3b were both highly colored, so it was easy to see their progress as they moved down the column during elution. More organic compounds are colorless in solution. How might you monitor the progress of a CC given a colorless sample?

Most organic polymers are named based on the monomers used in their production. However, poly(vinyl alcohol) (PVA) is NOT made from vinyl alcohol, but instead from vinyl acetate that is hydrolyzed after formation of the polymer. Why can’t we use vinyl alcohol in this polymerization? Draw the structure of vinyl alcohol to help you answer

Why do we use steam distillation to isolate eugenol rather than purify it by simple distillation?

Given that for 2 immiscible liquids like those used in this experiement, Calculatie the following for an oil (mwt = 169 g/mol) that distills during steam distillation at a boiling temperature of 98°C at 1 atm pressure

Pure octane has a boiling point of 125.7°C but can be steam distilled with water at a temperature of 90°C. Calculate the mass of octane that codistills with each gram of water and the percent composition of the vapor that is produced sduring the steam distillation

One synthetic preparation of aniline involves reducing nitrobenzene with iron and HCl and then steam distilling the resultant aniline at 99°C. How much aniline codistills with each gram of water using the steam distillation?

How could you isolate the R(+)-?-phenylethylamine from the mother liquor that remained after you crystallized and filtered off the S(-)-?-phenylethylamine

If the boiling point of the pure S(-)-?-phenylethylamine is 186-188°C , what is the boiling point of its enantiomer? What optical rotation would be observed if 3.72 g of the S(-)-amine were mixed with 3.72g of the (R)-amine?

Calculate the specific rotation of a substance that is dissolved in a solvent (0.35g/mL) and that has an observed rotation of -23° as determined with a 0.5 dm cell