ORGO 1 Lab FINAL
In the acid-base reaction from this experiment, what is the conjugate base?
sodium chloride
Why do we use wavenumbers (cm-1) instead of wavelength on the x-axis of the IR spectrum?
wavenumber is directly proportional to energy
While running an experiment, you are rushed for time and forget to dry your product. All methods of analysis indicate that no alcohol containing compounds were made. However, when you check using IR, you notice a broad absorption around 3200-3500 cm-1. If there is no alcohol, why is there still this absorption this region?
There is water in the sample
Which compound would be expected to show intense IR absorption at 2352cm-1?
C6H5CN
In TLC, the Rf value of a compound will increase the longer the plate resides in the solvent chamber.
False
IR spectroscopy provides valuable information about:
Functional Groups
How can compound Y, which has a higher boiling point than compound Z, elute before compound Z in a normal phase GC?
GC separates based on polarity as well
What is the leaving group in the substitution reaction 3?
H20
Rank the following compounds in order of their increasing pKa (lowest pKa to highest): water, methane, benzoic acid, HCl
HCl, benzoic acid, water, methane
Give 2 reasons or indications that the reaction was successful. These should be empirical observations immediately obtainable after reflux, not from instrumental analysis.
It no longer smells like wintergreen oil A solid is formed after acid addition
Imagine an organic liquid A has a density of 0.825 g/mL and is mixed with water. Assume this organic liquid does not dissolve in water, then the top layer must be:
Organic
Explain why it is important to use pencil when drawing your spotting line on the TLC plate?
Pencil markings do not run up the plate
The following data was collected from a TLC plate for 4 different compounds. The distance's traveled by each is shown below: Spot A: 8.2 cm Spot B: 0.7 cm Spot C: 6.5 cm Spot D: 1.3 cm The spotting line was placed 1.5 cm above the base and the solvent traveled 10.5 cm from the bottom of the plate. Calculate the Rf value for each compound. (0.5 point each)
0.911 0.078 0.722 0.144
A molecule has a molecular formula of C6H13O2N. What is the degree of unsaturation of this molecule?
1
What is the contribution of each keton function group (C=O) toward the degree of unsaturation of a molecule?
1
Assuming the reaction goes to completion, what is the theoretical yield, in grams, of benzoic acid (in grams) when using 1.84 grams of sodium benzoate? (MW of sodium benzoate is 144.1 g/mol, MW of benzoic acid is 122.1 g/mol)
1.56
What is the ideal pH for experiment 4 after adding acid 2 ? Explain what would happen if the acid wasn't added to make the pH in this range Yield would decrease .
2 Yield would decrease
Which of the following is/are possible product(s) for reaction 3?
2-chloro-2,4-dimethylpentane 3-chloro-2,4-dimethylpentane
If reaction one began with 1.6 g of alcohol starting material and you decide to use 2 equivalents of sodium bromide, how many grams of NaBr would you need? (NaBr molar mass=102.89 g/mol; SM molar mass=136.09g/mol) Answer with 2 decimal places. Enter the number only.
2.42
What ingredient of Panacetin is the most acidic and most easily ionizable in the presence of a base?
Acetylsalicylic acid
If you want to make 54 mL of 0.2 M NaOH solution, what mass (in grams) of NaOH would you need to dissolve? Use the molecular weight of NaOH as 40 g/mol
0.43
If the solubility of phenacetin is 1.22g/100mL solvent, how much solid (in grams) could be dissolved in 56 mL of solvent?
0.68
The following table shows data for a sample that was run under normal phase GC conditions: Peak Ret. Time Peak Area Peak 1 1.15 min 105 cm2 Peak 2 3.5 min 60 cm2 Peak 3 5.0 min 75 cm2 What is the percent composition of the most polar species? Answer to 2 decimal places. The running gas is not reported as a peak.
31.25
Each benzene ring has a contribution of ______ toward degree of unsaturation.
4
If you have 2.6g of an unknown, how much boiling water is needed to dissolve that substance? (solub. b.w. of unknown is 0.046 g/mL; density of water is 1.00 g/mL).
56.5 mL
The IR spectrum of a sample contains absorptions at 3050, 2950, and 1620 cm-1. To what class of organic compound does this sample most likely belong?
Alkene
Why is it important to slowly cool the product after recrystallization?
Allows perfect crystals to form, effectively removing all impurities
If methylene chloride has a density of 1.34 g/mL and was used in an extraction with an aqueous solution, which would be the top layer in the separatory funnel?
Aqueous
Name two pieces of equipment essential for carrying out vacuum filtration
Buchner funnel side-arm flask
Which of the following compounds would have the most downfield protons on an NMR spec?
Chloromethane
How could IR spectroscopy be used to distinguish between the following pair of compounds? C6H5CN vs. CH3CH2NH2.
Compound 1 has a nitrile peak at 2350 cm-1 Compound 2 has a N-H peak at 3300cm-1
How could IR spectroscopy be used to distinguish between the following pair of compounds? C6H6 (benzene) vs. C6H12 (cyclohexane)?
Compound 2 would have sp3 C-H less than 3000cm-1 Compound 1 would have sp2 C-H greater than 3000cm-1
Between the two compounds, isopentyl acetate and isopentyl alcohol, which compound will elute out first during Normal-Phase Gas Chromatography?
Isopentyl Acetate
Why is the water wash after finishing the heat under reflux procedural step so important?
It dilutes the acid
How would IR spectroscopy be used to quickly analyze the correct formation of product?
Loss of Ester peak Gain of Carboxylic acid peak
How will IR help us in our analysis to determine if we succeeded in making our product?
Loss of OH peak Presence of halogen peak
In the "Identifying a Constituent of "Panacetin" experiment, how are you determining the identity of the unknown?
Melting point
What is one way to identify a compound using instrumental analysis?
NMR Spectrometry
What results when too much solvent is used to dissolve the product in recrystallization?
Product loss - too much solvent dissolves more product
What are some of the disadvantages of using recrystallization? Select all that apply.
Products are always somewhat soluble - product loss is inevitable Identifying the proper solvent is difficult in most cases
Which reaction(s) have a rate that is determined by both the nucleophile and electrophile concentration?
Reaction 1 only
What is the purification method being used in Experiment 3?
Recrystallization
Briefly explain how do you determine if the organic layer is top or bottom with out knowing the density?
See which layer a drop of water migrates to
Which of the following is used to separate aqueous and organic liquids?
Separatory funnel
In each of the reactions, which is more water soluble: the starting material or the product? (Part Starting material ) Why? (Part Its functional groups H-Bond with water )
Starting material because its functional groups H-Bond with water
What compound is used as a catalyst for this experiment?
Sulfuric Acid
H2SO4 is a stronger acid than HCl. If H2SO4 is used to adjust the pH to 2, instead of HCl, how will this change affect the experimental result?
The amount of benzoic acid produced will not be significantly different
What change in the IR absorption pattern will tell you that you synthesized Isopentyl Acetate? (Note: Please give both the correct structural features that are present and absent, in relation to the Isopentyl Alcohol) The presence of a sharp peak at ~1700 cm^-1 will show the presence of a carbonyl
The lack of an OH peak around ~3400 cm-1 Sharp peak at ~1700cm-1 will show carbonyl
What issue would you run into if you used 100% 18M acetic acid as your TLC solvent in a normal phase TLC run?
The plate would not run
How IR may be used to help estimate the purity of your product? Select those that apply.
The presence of an OH peak IR is not quantitative - GC would be better for estimation
What is the purpose of "washing" the reaction mixture with dilute NaHCO3? Why does it require more attention than usual to venting? Select all that apply.
To remove acid Bicarb makes CO2
Acetaminophen is the chemical name of what common drug?
Tylenol
Why do you use cold rinse water when vacuum filtering the benzoic acid product?
Using cold water will improve yield
Which compound is the most polar Vitamin C ? Which compound will have the highest Rf value Vitamin A ?
Vitamin A
Vitamin A, vitamin B, and vitamin C are three important biological supplements. Vitamin C is the most water soluble. Vitamin A is the least water soluble. Vitamin B is in between.
Vitamin C
On your first go, you decide to reflux, wash and separate. To check what you have made, you run a quick IR, which you think suggests that you have a mixture of starting material and product, so you decide to purify by distillation. The product you obtain is much purer, but you note you have a very low yield and not enough to run an HNMR sample. What is the most important thing you should change experimentally for next week?
WHICH ONE IS IT? dry with sodium sulfate before distilling use more starting material in the intial reaction increase the equivalents of halogen from 2.5 to 3 reflux at a higher temperature
Which would be a suitable gas to use for the mobile phase of a reverse phase GC?
Water vapor
When recrystallizing, it is important to have an appropriate solvent. Select all that are characteristics of a good solvent.
When hot, the solvent dissolves a large amount of the compound Inexpensive Is volatile enough that crystallized solid can be dried Completely dissolves impurities Does not react chemically with the compound
Which of the following is the rate law for the reaction 3 mechanism?
rate = k[alkyl halide]
In Exp. 1, what is the most notable observable physical trait of the chemical reaction that signals its progress toward the product?
change in state of matter
What is the purpose of using sodium sulfate in the banana oil experiment?
drying the liquid
Which of the following outcomes would most possibly occur if you acidified sodium acetylsalicylate to pH 4 instead of pH 2?
falsely low % recovery of aspirin
Which of the following outcomes would most possibly occur if you initially dissolved the panacetin mixture in a more polar organic solvent, still immiscible in water, instead of dichloromethane?
falsely low % recovery of sucrose
The region of the of the IR spectrum which contains the most complex vibrations (600-1400 cm-1) is call the .
fingerprint region
If an impurity exists in a sample, the melting point _________ and ________.
lowers and broadens
As in part B of exp. 1, when trying to determine the density of an unknown compound by graphing, what is recorded on the y-axis?
mass
Drawing arrows to explain electron movement in organic chemistry is known as a (an):
mechanism