PROB_SET_1 - CEM 251 Spring 2008 1st Problem Set (Chapters...

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Unformatted text preview: CEM 251 Spring 2008 1st Problem Set (Chapters 1-6) 1. For the following molecule: O Br C N the number of sp3 carbons is: the number of sp2 carbons is: the number of sp carbons is: the hybridization of N is: the hybridization of O is: the number of s bonds is: the number of p bonds is: the molecular formula is: 2. Calculate the formal charge on each atom in the following structure. CH2 N N 3. For a carbocation, carbon radical and carbanion: a) How many unshared electrons are associated with the central carbon? b) How many s bonds are attached to the central carbon? 4. How many of the methyl groups will occupy an equatorial position in the more stable chair conformation of the following molecules? Which configuration should be most stable of the four? CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 5. a) Draw a Newman projection of the most stable conformation of 2–methylhexane down the C2–C3 bond. Draw Newman projections of the two chair conformations of trans-1-ethyl-3methyl-cyclohexane viewed simultaneously down the C3–C4 and C1–C6 bonds. Draw a wedge-dotted line structure for molecule X. CH3 H H H b) c) H H H CH3 X d) Draw a wedge-dotted line structure for molecule Y. CH3 H CH3 H Y 6. Give the isomeric relationship between the following pairs of molecules. Your choices are constitutional, configurational, conformational or identical. CH3 H CH3 a) H H CH3 CH3 CH3 H CH3 and CH3 H CH3 H CH3 CH3 b) CH3 and CH3 H CH3 CH3 H CH3 c) H and CH3 H CH3 CH2 CH3 H H H H CH3 d) H H and H CH2 CH3 H CH3 e) H H CH3 H H and H CH2 CH3 CH3 H H CH2 CH3 H CH2 CH3 f) CH2 CH3 and CH3 7. Acid H3O+ CH3CO2H H2O CH3OH pKa –1.5 5.0 16 17 Using the above table of acid strengths, answer the following questions: a) Which is the stronger acid, acetic acid (CH3CO2H) or water? b) Which is the stronger base, water or sodium acetate (CH3CO2Na)? c) Which is the stronger base, sodium hydroxide or sodium methoxide (NaOCH3)? d) Label the acids and bases in the following equations and encircle the side favored at equilibrium. CH3CO2H + NaOH CH3OH + H2O e) CH3CO2Na + H 2O CH3O H3O Can one use the reaction of sodium hydroxide with methanol (CH3OH) to prepare sodium methoxide? Can one use the reaction of sodium hydroxide with acetic acid to prepare sodium acetate? f) 8. Which of the following olefins possess configurational isomers? a) c) e) 1-hexene 2–methyl–1–hexene 3–methyl–2–hexene b) d) f) 2–hexene 2–methyl–2–hexene 3–hexene 9. Which of the following represent Z–3-methyl–2–pentene? Which represent E–3–methyl–2–pentene? CH3 CH2 C CH3 C CH3 CH3 C H CH3 CH2 C H CH3 C CH3 H C CH3 a b c CH2 CH3 CH3 C CH3 CH2 C H CH3 H C CH3 C CH2 CH3 CH3 H C CH3 C CH3 CH2 CH3 d e f 10. Label the following cations as 1°, 2°, or 3°. Indicate the most stable cation in each group: C H3 (+) a) C H3 C H2C H2C H3 A C H2C H3 C H3C H2 C H C H C H2C H3 C H3C H2 B C H2C H3 (+) (+) C H2 (+) C H C H2C H2C H3 C C H2C H2(+) C H3C H2 b) (+) H A B C 11. Draw the structure of the faster-formed carbocation intermediate in the following reactions: C H3 a) C H3 C H3 HBr C H3 C H3 C C H C H3 CH C H3 HCl b) 12. Draw energy diagrams for the formation of both products of the following reaction (assume the 1° chloride is more stable than the 2° chloride): C H3C H2C H C H2 + HCl 13. For the following energy diagram: A B a) b) Which product, A or B, is formed faster? Which product, A or B, is more stable? ...
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This note was uploaded on 03/29/2008 for the course CEM 251 taught by Professor Rathke during the Spring '07 term at Michigan State University.

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