CHEM 238 Final Exam Questions with 100%
Correct Answers
Which of the following components of the atmosphere can react with a Grignard
reagent?
oxygen; water; carbon dioxide; nitrogen
oxygen, water, carbon dioxide (contain acidic hydrogens; H must be connected to carbon
next to double/triple bond, a ketone, or an EN atom like oxygen)
What is a positive 2,4-DNP test result?
immediate formation of orange precipitate
What is a positive Br₂ test result?
red color disappearing
What is a positive iodoform (I₂/OH⁻) test result?
yellow color (formation of precipitate, but usually is so dilute that only the color is clearly
seen)
What does 2,4-DNP test for?
aldehydes and ketones
What does Br₂ test for?
alkenes
What does iodoform (I₂/OH⁻) test for?
methyl ketones (or methyl alcohols like CH₃CH₂OH)
, TLC is a technique easily used for:
a. the qualitative monitoring of reactions
b. the quantitative monitoring of reactions
c. purification of large amounts of an impure compound
d. evaluation of the purity of a starting material
e. a and d
e. a and d
[the qualitative monitoring of reactions (compare Rf spots of samples of the reaction at
t=0,10,20) and the evaluation of the purity of a starting material (compare Rf value to
literature)]
Using semi-empirical calculations with Spartan, which of the following were computed
in the Molecular Modeling II lab?
I. Transition state structure
II. Heat of formation
III. Distribution of Charge
IV. Product Ratios
II. Heat of formation and III. Distribution of Charge
(other two were discussed but not computed using the software)
The reaction of C₆H₅MgBr with water produces:
a. C₆H₆
b. C₆H₅OH
c. C₆H₅Br
d. diphenyl
e. all of these
Correct Answers
Which of the following components of the atmosphere can react with a Grignard
reagent?
oxygen; water; carbon dioxide; nitrogen
oxygen, water, carbon dioxide (contain acidic hydrogens; H must be connected to carbon
next to double/triple bond, a ketone, or an EN atom like oxygen)
What is a positive 2,4-DNP test result?
immediate formation of orange precipitate
What is a positive Br₂ test result?
red color disappearing
What is a positive iodoform (I₂/OH⁻) test result?
yellow color (formation of precipitate, but usually is so dilute that only the color is clearly
seen)
What does 2,4-DNP test for?
aldehydes and ketones
What does Br₂ test for?
alkenes
What does iodoform (I₂/OH⁻) test for?
methyl ketones (or methyl alcohols like CH₃CH₂OH)
, TLC is a technique easily used for:
a. the qualitative monitoring of reactions
b. the quantitative monitoring of reactions
c. purification of large amounts of an impure compound
d. evaluation of the purity of a starting material
e. a and d
e. a and d
[the qualitative monitoring of reactions (compare Rf spots of samples of the reaction at
t=0,10,20) and the evaluation of the purity of a starting material (compare Rf value to
literature)]
Using semi-empirical calculations with Spartan, which of the following were computed
in the Molecular Modeling II lab?
I. Transition state structure
II. Heat of formation
III. Distribution of Charge
IV. Product Ratios
II. Heat of formation and III. Distribution of Charge
(other two were discussed but not computed using the software)
The reaction of C₆H₅MgBr with water produces:
a. C₆H₆
b. C₆H₅OH
c. C₆H₅Br
d. diphenyl
e. all of these
