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1H NMR Correlation Chart: Table of 1H Chemical Shifts
Type of Hydrogen Chemical Shift Range in ppm R-??CH3 0.7 -?? 1.3 R-??CH2-??R Type of Hydrogen O
R 1.2 -?? 1.4 C
O OH C O R R3CH R C C H
R O O H C C C C H C S R H S H 4.5 ? 6.5 6.5 ? 8.0 S O C
H O 1.7 ? 2.7 C H
C R O Cl H
C H I 9.0 ? 10.0 H O C C
H 3.1 ? 4.1 H 2.7 ? 4.1 H H 4.0 ? 7.0a 4.2 ? 4.8 H H 0.5 ? 5.0a Br O H H H 3.0 H H 3.2 ? 3.8 H 1.0 ? 4.0a R H O
R H 2.0 -??3.0 H H 4.1 ? 4.3 H H 2.3 -??2.7 H
O H F R H H 2.1 ? 3.0 H C 2.2 ? 2.9 H C 3.0 ? 5.0a NO2 H H N H R N 5.0 ? 9.0a 0.5 ? 4.0a 2.1-?? 2.5 C C H H C H
H H R N H H C H H H C R R H
N N 2.1 ? 2.4 H C C C H O H
R R H H H C O 1.6-?? 2.6 C 3.5 ? 4.8 H H 1.4 ? 1.7 H Chemical Shift Range in ppm 11.0 ? 12.0 2.0 ? 4.0 H R C H Concentration, temperature, and solvent will influence these shift a 1 IR Correlation Chart:
N-H stretch 3300-2500
1320-1000 O-H, stretch
H-C=O, C-H stretch
C(triple bond)N, stretch
-C(triple bond)C-, stretch
C-O, stretch Table of Recrystallization Solvents Solvent Boiling Point 0C Benzene 80 Functional Group
Primary, secondary amines,
Alcohols, carboxylic acids,
esters, ethers Ethanol 78 Ethyl Acetate Chloroform Water Hexane Cyclohexane Petroleum Ether Methanol 77 61 100 69 81 50 64.5 Toluene Tetrahydrofuran (a cyclic ether) Acetonitrile Dichloromethane Diethyl ether 110 66 Types of Compounds it solubilizes Slightly polar and nonpolar aromatics General, esters, nitro and bromo compounds General, esters Slightly polar compounds Amides, some carboxylic acids Nonpolar compounds Nonpolar compounds Nonpolar compounds General esters, nitro and bromo compounds Slightly polar aromatics Slightly polar compounds 82 40 35 Polar Compounds Slightly polar compounds Slightly polar compounds 2 Chem 203 Name______________________________________________Section:______TA:_______________________ LA Problem Set 10
Must be completed and signed by a LA or Dr. B. by no later than December 7th to obtain a signature to
receive homework or extra credit for this problem set 1. This mechanism consists of four of the elementary steps. These steps are listed below in order. Draw the arrows for the electron pushing mechanism based on the Aldol Condensation shown below. Do not forget to include all lone pairs and formal charges. (40 pts) O O
CH3 BP 202 0C H3C + Na+ -OH
H H3C CH3
BP 74 0C i) Proton Transfer between molecules ii) Nucleophilic Addition iii) Proton Transfer between molecules iv) E2 Elimination O
BP 231 0C CH
3 3 Extra Mechanism Problem: Note the exam will only have 1 of these types of questions This mechanism consists of five of the elementary steps. These steps are listed below in order. Draw the arrows for the electron pushing mechanism based on the Transesterifcation Reaction shown below. O
+ O H2SO4 + OH O i) Protonation ii) Nucleophilic Addition iii) Intramolecular Proton Transfer iv) Nucleophilic Elimination v) Deprotonation 4 2. Reaction Workup. Use a flow chart diagram to describe the steps you would follow to isolate the product mixture in the reaction below (20 pts). Make sure you include all the steps and reagents used in the isolation process. Then describe how you would purify (20 points) and characterize (20 points) the product. Be specific with your purification (technique and conditions) and characterization information (key data). (60 pts total) OH
H 2SO 4 +
H 2O 2-Methyl-1-phenyl-1-propanol
Bp 250-253 0C, slightly water soluble 2-Methyl-1-phenyl-1-propene
Bp 187-188 0C, water insoluble 5 3. The following questions are related to the techniques used this semester. In each case troubleshoot the situation and explain what may have gone wrong. (25 pts) Note: Make sure you highlight what went wrong and what you would do to correct the situation. a. A reaction is carried out in a 50 mL round bottom flask and when it is complete, you can clearly see 2 distinct layers. After transferring the mixture to a separatory funnel you decide to add ether and then shake to ensure that all the organic compounds are in the organic layer. After shaking you let the separatory funnel sit in a ring stand and there is only 1 layer. Even after sitting 10 minutes only one layer is visible. What happened and can you do anything to fix it? (10 pts) b. The product from the reaction above has a boiling point over 200 0C. You isolated 5 g of organic material after drying and evaporating the ether from the organic layer. You know the product mixture most likely contains starting material so you decide column chromatography would be the best method for purification. You find a mobile phase for the separation of this mixture using TLC and you were able to see a spot for the starting material and the product and their Rf values are 0.5 units apart. You pack the column you have in your lab locker and load all the organic mixture dissolved in a small amount of hexane on the column. You check every fraction that you isolate from the column using TLC and the product and starting material appear in every fraction. If the compounds separated well on the TLC why did they fail to separate it on the column? (10 pts) c. You decide to analyze an oily product isolated from a reaction by NMR. You add approximately 0.5 mL of deuterated chloroform to 35 mg of the oil and transfer it to an NMR tube. After adequate mixing you notice that there are globs that did not dissolve in the chloroform. What could be the cause of these globs and will they prevent you from obtaining a spectrum? (10 pts) d. You have a product mixture of alkenes from a dehydration reaction and the boiling points of the alkenes are: 1-??methyl cyclohexene: 110 0C, 3-??methyl cyclohexene: 104 0C, 4-??methyl cyclohexene: 102 0C. You decide to run a fractional distillation to separate the products and you only have 2 distinct fractions of distillate, one at 102 0C and the other at 109 0C. What happened to the third fraction? 6
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