chemistry 123: physical and organic chemistry midterm 1 febuary · pdf file ·...

Chemistry 123: Physical and Organic Chemistry Midterm 1 Febuary 6, 2009

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Name: ______________________

1) Name the following compounds or draw the structure in the box beside the name.

/50 Total Marks

(2E)-4-methylpent-2-ene

4-fluoropentan-2-one

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butanoic acid

3 Chloro- N-ethylhexan-2-amine


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2) A sample of (2S)-2-bromo-3-methylbutane has a specific rotation ([α]D) of +10.4° It is reacted with HCl to produce a new product that is then isolated and has a measured specific rotation of -10.4°. Explain the reaction mechanism (with appropriate “arrow pushing”). Name the final product.

This must be an SN2 reaction as the steriocenter is reversed. 3) If the specific rotation of the product described in Question 2 was +0°, what would that indicate? How about if it was +5.2°? If the rotation was zero, it would indicate either SN1 reaction. If +5.2, this would indicate either incomplete reaction of mixed SN1 and SN2.

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4) Toluene reacts by a electrophilic addition reaction with Hydrogen Fluoride (HF) at position 4 on the aromatic ring. Show the mechanism with appropriate arrow pushing. Name the final product and indicate any stereocenters. 5) Draw and name the most stable conformation of dimethylcyclobutane. Justify your answer

Place substituents as far apart as possible for most stable

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/4

S

Marking: 2 marks for proper mechanism, 2 for proper arrows (-0.5 per error) . 1 for name and 1 for correct steriochemistry

Marking: 2 marks for valid structure. 1 mark for correct conformer, 1 for explaination


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Marking: 2 marks for each eclipsed, 2 marks for distinction between gauch forms. 2 marks for clearly indication of reason

6) Sketch a series of Newman projections looking from Carbon 2 to 3 for 2-bromo-3-methylbutane. Indicate the most stable and the least stable eclipsed forms. Will the gauche forms have different energies? Explain using diagrams.

7) Indicate(*) all the steriocenters in the following molecules. For each molecule provide the correct R/S notation on at least 3 of these Steriocenters.

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Marking: 0.5 marks per correct steriocenter. 0.5 mark per correct R/S


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Multiple Choice (circle best answer) 8) Which of the following compounds does not have the molecular formula C6H14O? A) 1-hexanol B) 2-hexanol C) 3-methyl-2-pentanol D) cyclohexanol 9) The eclipsed and staggered forms of ethane are said to differ in: A) molecular formula B) configuration C) conformation D) constitution . 10) Which conformations of butane are the most stable? A) gauche only B) eclipsed and totally eclipsed C) gauche and anti D) eclipsed only 11) Which of the following correctly ranks the cycloalkanes in order of increasing ring strain per methylene? A) cyclopropane < cyclobutane < cyclohexane < cycloheptane B) cyclohexane < cyclopentane < cyclobutane < cyclopropane C) cyclopentane < cyclobutane < cyclopentane < cyclopropane D) cyclopentane < cyclopropane < cyclobutane < cyclohexane? 12) What is the relationship between the following compounds?

A) constitutional isomers B) enantiomers C) diastereomers D) conformational isomers

13) Is the molecule shown below chiral or achiral??

A) Chiral (B) Achiral

14) What product results from the SN2 reaction between (R)-2-chloropentane and hydroxide? A) (R)-2-pentanol B) (S)-2-pentanol C) racemic pentanol D) 1-pentanol

/10 (1 point each)


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15) Which of the following functional group has higher priority with regard to naming based on IUPAC rules? (A) Amide (B) Amine (C) Nitrile (D) Alcohol

16) Tautomerization is ? (A) when two isomers tease or collide but do not react (B) isomers that differ by position of a hydroxyl group (C) isomers that differ by the location of a H and a double bond (Tautomer def) (D) Isomers that differ based on ring strain (E) None of these

17) A meso compound is ? (A) composed of 2 groups (B) Achiral (C) Very small (D) A rotomer (E) None of these

chemistry 123: physical and organic chemistry midterm 1 febuary · pdf file ·...

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