CHEM 122: Introduction to Organic Chemistry Homework 4 (Thursday May 6): Chapter 5: Alcohols, Ethers, and Thiols. (15 problems) Chapter 6: Chirality: The Handedness of Molecules. (8 problems) Chapter 5: 1. Explain in terms of noncovalent interactions (intermolecular forces) why the lowmolecular-weight alcohols are more soluble in water than the low-molecular-weight ethers. 2. Show hydrogen bonding between the oxygen of diethyl ether and a hydrogen of water. 3. From each pair, select the compound that is more soluble in water. a) CH3OH or CH3OCH3 OH b) CH3CHCH3 CH2 or c) CH3CH2CH2SH CH3CCH3 or CH3CH2CH2OH 4. Give the structural formula of an alkene or alkenes from which each alcohol can be prepared. a) 2-Butanol b) 1-Methylcyclohexanol c) 3-Hexanol d) 2-Methyl-2-pentanol e) Cyclopentanol 5. Write equations for the reaction of 2-butanol with these reagents. a) H2SO4, heat b) K2Cr2O7, H2SO4 6. Show how to convert cyclohexanol to these compounds. a) Cyclohexene b) Cyclohexane c) Cyclohexanone d) Bromocyclohexane 7. Show reagents and experimental conditions to synthesize each compound from 1propanol. Br Br Br (e) (d) OH (b) (f) O (c) (a) OH (g) OH O (i) (h) O H 8. Write the common name for each ether. O a) b) [CH3(CH2)4]2O c) CH3CHOCHCH3 9. Write the IUPAC name of each thiol. SH a) CH3CH2CHCH3 b) CH3CH2CH2CH2SH c) 10. Write the common name for each thiol in Problem 9. 11. Explain why methanethiol, CH3SH, has a lower boiling point (6oC) than methanol, CH3OH (65oC), even though methanethiol has a higher molecular weight. 12. Draw structural formulas and write common names for the six isomeric ethers with the molecular formula C5H12O. 13. Show how to prepare each compound from 2-methylcyclohexanol. O CH3 a) b) CH3 d) CH3 OH CH3 c) 14. The mechanism of the acid-catalyzed dehydration of an alcohol to an alkene is the reverse of the acid-catalyzed hydration of an alkene. The dehydration mechanism occurs by the following three steps: Step 1: Add a proton. Step 2: Break a bond to form stable molecules or ion. Step 3: Take away a proton. These three steps are illustrated here by the dehydration of 2-butanol to give 2-butene. Use curved arrows to show the flow of electrons in each step; that is, show how each bond-making or bond-breaking step occurs. OH Step 1: H+ H O H H O H Step 2: + H2O Step 3: and H + H+ 15. Use the reactions we learned in Chapter 3 and this chapter to show how to bring about the following chemical transformations. Some transformations will require only one step. Others will require two or more steps. OH a) HO b) O c) OH Br d) O CH2OH OH e) CH3 f) OH Chapter 6: 1. Which of the following objects are chiral (assume that there is no label or other identifying mark)? a) Pair of scissors b) Tennis ball c) Paper clip d) Beaker e) The swirl created in water as it drains out of a sink or bathtub. 2. 2-Pentanol is chiral, but 3-pentanol is not. Explain. 3. 2-Butene exists as a pair of cis-trans isomers. Is cis-2-butene chiral? Is trans-2-butene chiral? Explain. 4. Which of the following compounds contain stereocenters? a) 2-Chloropentane b) 3-Chloropentane c) 3-Chloro-1-butene d) 1,2-Dichloropropane 5. Which of the following compounds contain stereocenters? a) Cyclopentanol b) 1-Chloro-2-propanol c) 2-Methylcyclopentanol d) 1-Phenyl-1-propanol 6. Draw the mirror image for each molecule: COOH H H2 N C H CH3 a) OH b) CH 2 OH O OH H H OH H HO H H OH c) H3 C NH2 d) 7. Mark each stereocenter in these molecules with an asterisk. Note that not all contain stereocenters. OH CH3 O N CH3 a) OH b) O O OH c) NH 2 d) 8. Which of the eight alcohols with a molecular formula of C 5H12O are chiral?
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