Chemistry 29b M. Walker
Practice Test
190 points total. Duration 60 minutes. All questions are worth 9 points unless stated. If you believe several answers are possible, choose the best single option.
1. Why is sulfuric acid used along with nitric acid, for the nitration of methyl benzoate?
(a) If nitric acid alone were used, the ester would not protonate and therefore would not dissolve.
(b) Sulfuric acid helps in the generation of the nitronium cation, a key intermediate for the reaction.
(c) Sulfuric acid helps in the generation of the protonated form of the ester, a key intermediate in the reaction.
(d) Sulfuric acid performs a sulfonation reaction, and the nitric acid reacts with the resulting sulfonic acid.
2. (18 points) In a preparation of 1,4-di-tert-butyl-2,5-dimethoxybenzene, 304 mg of 1,4-dimethoxybenzene (MP 57 oC, MW 138 g/mol) was reacted with 296 mg of tert-butyl alcohol (MP 26 oC, MW 74 g/mol) in the presence of excess acetic and sulfuric acids.
Part I: What would be the maximum mass of product that could be isolated?
_______________________________
Part II: What would be the maximum mass of product if only 274 mg of 1,4-dimethoxybenzene were used?
_______________________________
3. In the preparation of methyl 3-nitrobenzoate, the crude product was washed with ice-cold methanol, which helps to remove water and avoid oil formation during the recrystallization step.
TRUE or FALSE
4. Phenylmagnesium bromide reacts with water to produce
_______________________________
5. When 1,4-dimethoxybenzene, acetic acid and tert-butyl alcohol are mixed then cooled to 0 oC, the mixture forms a thick slush. This is caused by:
(a) Formation of tert-butyl acetate, which is a gelatinous solid.
(b) Formation of 1,4-di-tert-butyl-2,5-dimethoxybenzene which precipitates.
(c) Formation 1-tert-butyl-2,5-dimethoxybenzene which precipitates.
(d) The tert-butyl alcohol and acetic acid beginning to freeze.
(e) Water produced in the reaction coming out as ice.
6. What is the solvent used for the reaction of diphenylacetylene with tetraphenylcyclopentadienone?
___________________________________
7. Aldehydes and ketones can be distinguished using their DNP derivatives, which are always orange for aldehydes and yellow for ketones.
TRUE or FALSE
8. A compound X, of formula C8H8O, forms a highly colored DNP derivative but gives a negative Tollen's test. Compound X reacts with NaOH/I2 to give iodoform and the sodium salt of a carboxylic acid, Y. The UV spectrum of compound Y indicates that there is no simple conjugated diene, and the IR spectrum does not contain an alkyne. Draw the structure of X.
___________________________________
9. The success of the Fischer esterification usually depends on:
(a) The formation of a stable aromatic system
(b) An ester with a boiling point lower than the starting alcohol
(c) Formation of a silver mirror
(d) Azeotropic removal of water
(e) Fresh carnations left at Fischer’s grave.
10. In the Diels-Alder experiment, which of the following is true?
(a) The high temperatures favor products with higher entropy, and this helps the initial Diels-Alder reaction of diphenylacetylene with tetraphenylcyclopentadienone to form a bicyclic intermediate.
(b) The high temperatures favor products with higher entropy, and this helps drive the collapse of the bicyclic intermediate (with loss of CO) to give hexaphenylbenzene.
(c) The loss of CO is irreversible because it is lost into the air, and this helps drive the collapse of the bicyclic intermediate to give hexaphenylbenzene.
(d) Both answers (a) and (c).
(e) Both answers (b) and (c).
11. To what chemical class does nylon belong?
(a) Amide
(b) Amine
(c) Alcohol
(d) Alkane
(e) Acid chloride
12. What was the base used in the formation of the Wittig reagent in experiment 8?
___________________________________
13. In the preparation of nylon, what remains in the aqueous solution after the nylon strand has been removed?
(a) HCl, and any unreacted diamine
(b) HCl, NaOH and any unreacted diamine
(c) NaCl, NaOH and any unreacted diamine
(d) NaOH only
(e) Thionyl chloride and NaOH
14. The purpose of preparing derivatives (such as dinitrophenylhydrazones) is to provide an additional form of characterization.
TRUE or FALSE
15. What impurity is removed from crude triphenylmethanol (made via the Grignard reaction) using a trituration in petroleum ether?
___________________________________
16. (12 points) Isobutyl formate, HCOOCH2CH(CH3)2, is an ester that supposedly smells of raspberries.
Part I: How many types of hydrogen are expected in the NMR spectrum of isobutyl formate?
___________________________________
Part II: What is the multiplicity of each peak in the NMR spectrum?
___________________________________
17. (34 points) Compound X has the formula C10H12O2 and the NMR spectra (1H, 13C) attached. Deduce a structure for X. [1H Spectrum from Univ Potsdam, Ger.]
NOTE: I only have 1H at present. The 13C spectrum contains eight different peaks, of which three come below 100 ppm. One of the peaks is small and comes around 200 ppm.
No. of double bond equivalents = _______________________
How many types of hydrogen are there? ________________________
How many types of carbon are there? _____________________
How many of these carbons are likely to be sp2? ______________________
What no. of hydrogens is present at what chemical shift?
________ at _________ ppm ________ at _________ ppm
________ at _________ ppm ________ at _________ ppm
________ at _________ ppm ________ at _________ ppm
________ at _________ ppm ________ at _________ ppm
What prominent groups are present in the 1H spectrum? [Continue overleaf]
What is the structure of X?
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