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This 11 page Class Notes was uploaded by Cole White IV on Monday October 5, 2015. The Class Notes belongs to CHEM32 at City College of San Francisco taught by JamesArmstrong in Fall. Since its upload, it has received 46 views. For similar materials see /class/219529/chem32-city-college-of-san-francisco in Chemistry at City College of San Francisco.
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Date Created: 10/05/15
CHAPTER 9 ANSWERS TO SELECTED PROBLEMS SAMPLE PROBLEMS Try it yourself CH3 CH3 91 CH3 CH CHCH3 and CH3 CHCHzCH2 OH OH 92 a Ethylene gives only one product because the two sides of the ethylene molecule are identical OH OH CHz CH3 and CH3 CH2 are the same molecule b CisZhexene gives two different products as shown below OH OH CH3 CH CH2CHzCHzCH3 and CH3 CH2CH CH2CH2 CH3 93 2butanol OH CH 94 CH3CH2CHCH2CH2CH2CH2CHzCH3 W 95 Cyclohexanol has the higher boiling poing because it can form hydrogen bonds while cyclohexene cannot The two molecules are roughly the same size so we can ignore the size in this question 96 3pentanol is more soluble than propane because the alcohol group in 3pentanol can form hydrogen bonds Propane does not contain any atoms that can form hydrogen bonds 97 Compound X is the least soluble followed by compound Y followed by compound Z the most soluble CH3 98 CH2CH C CH3 CH3 CH3 CH3 99 CH3CHz CCH CH3 and CH3CHz CH CHCH2 910 This compound does not contain a phenol group because the hydroxyl group is not directly bonded to the aromatic ring 911 Compound Y is the least soluble followed by compound X followed by compound Z the most soluble SECTION PROBLEMS Section 91 OH CH3 OH CH3 91 a CH3 CH CHz CH CH3 and CH3 CHz CH CH CH3 OH OH b CHzCHzCHzCH3 and CH3 CH CHzCH3 OH Only one product is formed because the 0 CH339CH239CH39CH239CH239CH3 two sides of cis3hexene are identical OH CH d 0 CHZ CH3 and Egtc1 CH3 OH OH e HzCH3 and OLCHzCH3 92 In part b the second product will predominate In part d the rst product will predominate In part e the second product will predominate 93 Alkenes b and e form only one product when they react with water because the two sides of the molecule are identical when you diVide the molecules in half through the CC bond CH3CHz CH 39EIICH CHz CH3 Section 92 94 Most biological reactions are linked in a sequence If the enzyme does not select the correct product the next enzyme cannot use the product in the next reaction so the incorrect product goes to waste 95 O OH H HO C CHz C CHz C OH 0 C OH H 0 Section 93 96 a lbutanol b cyclohexanol c 4octanol d lpentanol CH OH 97 a CH3 CH2 CH CH2CH3 b CH3CHCH2CH2CH2CH2CH2CH2CH3 OH 0 If 1 aw 98 a This name is incorrect because it does not tell where the alcohol group is located b This name is correct c This name is correct d This name is incorrect because the principal chain must be numbered from the end that is closest to the functional group The correct name would be 2pentanol Section 94 99 5 5 H f Hj 1gt CH3 CH2 CH2 CH3 910 a 3pentanol has a higher boiling point than pentane because it contains a functional group that can form hydrogen bonds b The second compound has the higher boiling point because it contains two alcohol groups both of which can form hydrogen bonds 911 a 2butanol has the higher solubility because it has the smaller hydrophobic region b 2butanol has the higher solubility because it contains a group that can form hydrogen bonds while hexane does not c Ethanol has the higher solubility because it contains a group that can form hydrogen bonds while ethyne does not 912 a The solution is basic because KOH dissociates into K and OH ions and OH ion is a strong base b This solution is neutral because CH30H methanol does not dissociate into ions c This solution is basic because BaOHz dissociates into Ba2 and OH ions Section 95 913 a CH2CH2 This is the only product b CH2CH CH2CHzCH3 and CH3 CH CH CHzCH3 Both the cis and the trans isomers of the second alkene will be formed CH3 CH3 c CH3 CCH CHzCH3 and CH3 CH CHCH CH3 Both the cis and the trans isomers of the second alkene will be formed CH3 d CH3 C CHCH CH3 This is the only product but both the cis and the l trans isomers will be formed CH3 e Methanol cannot be dehydrated because it does not have a second carbon atom adjacent to the functional group f 6 This is the only product CH3 OH CH3 OH 914 CH3 CH CH2CH CHzCH2CHzCH3 and CH3 CH CH2CHzCHCH2CHzCH3 915 In a dehydration reaction there must be at least one hydrogen atom directly bonded to the carbon adjacent to the functional group In this molecule the adjacent carbon is not bonded to a hydrogen atom This carbon atom is not bonded to a OH I hydrogen atom Section 96 9 1 4 SH OH OH OH 6 b CH3 thiol alcohol phenol alcohol 915 a Phenol has a higher solubility than benzene because the hydroxyl group in phenol can form hydrogen bonds b The second molecule lpropanol has a higher solubility than the first a thiol because alcohol groups can form hydrogen bonds while thiol groups cannot 916 Compounds b and d can be dehydrated Phenols and thiols cannot be dehydrated CUMULATIVE PROBLEMS Odd numbered problems only 919 a There are many possible answers Here are two gt OH H l l Cyc aprapana cyclohexanol b There are three possible answers SH SH SH CHzCHzCH3 CH3 CH CH3 c There are many possible answers Here are two CH CH CH3 CH3 C CH3 CHzCHzCHzCH CH3 CH3 d There are many possible answers You can either move the functional group to a different location or convert the principal chain pentane into a branched chain CH OH CH3 CH3 CH CHzCHzCH3 CHzCHzCH CH3 Here we have moved the Here we have changed the functional group from the 1 unbranched carbon chain carbon to the 2 carbon into a branched chain OH 921 a CH3 CH2 This is the only product b CH3 CH CH2 This is the only product c CH3 CH CH2 This is the only product OH CH d D CHzCHzCHZ and D CHzCH CH3 e CH3 CHC CH3 and CH2CH CH CH3 CH3 CH3 CH3 f CH2CH C CH3 This is the only product CH3 g This alcohol cannot be dehydrated because there is no hydrogen atom on the carbon adjacent to the functional group OH h CH3 CHzCH CHzCH2CH3 This is the only product i This is the only product OH OH j EgtLCH3 and H 3 k There are three products of this dehydration Egtc cHzcHzcHzCH3 O TCH CH2CH2CH3 CH3 AH C CHzCHzCHzCH3 CH2 OH 923 d The main product is IgtCH2HCH3 OH j The main product is 04cm 925 a methanol b 2butanol c phenol d 3octanol e cyclohexanol OH CH 927 a CH3 CH2 b CH3 CH CH2CHzCH3 OH OH I c E d CH3 CH CH3 OH e CHzCHzCHzCHzCHzCH3 929 a C3H80 b C3H50 931 a The rst molecule is more soluble because it contains a functional group that can form hydrogen bonds the alcohol group while the second molecule does not b The rst molecule is more soluble for the same reason as part a The thiol group does not form hydrogen bonds c The second molecule is more soluble for the same reason as part a d The rst molecule is more soluble Both contain an alcohol group but the rst molecule has the shorter hydrocarbon chain e The second molecule is more soluble because it contains a functional group that can form hydrogen bonds while the first molecule does not The chain length only matters when both molecules contain hydrogenbonding groups f The second molecule is more soluble because it contains two functional groups that can form hydrogen bonds while the first molecule only contains one 933 a Compound C has the lowest solubility in water because it cannot form hydrogen bonds b Compound B can be dehydrated Thiols and phenols cannot be dehydrated 935 Enzymes speed up reactions so they occur at a rate that is useful to the cell When more than one product is possible enzymes also select the correct product ensuring that the cell does not waste its resources H 6 6 6 H 5 0 9 i elf 9 Here methanol is the donor and water is the acceptor Here water is CH3 the donor and methanol is the acceptor 939 Isomers have the same molecular formula but different structures and different names a These two molecules are isomers b These two molecules are not isomers they are two different ways to draw the same compound 2butanol c These two molecules are not isomers because they have different molecular formulas The second molecule has five carbon atoms while the first molecule has only four d These two molecules are isomers e These two molecules are isomers Isomers do not have to have the same functional groupithey only need to have the same molecular formula f These two molecules are not isomers The first molecule has 12 hydrogen atoms while the second has only 10 941 Reaction 2 has two possible products so the enzyme must select the correct product 943 There are four possible products OH CH CH CH CH3 CH CH2CHzCH CH3 CH3 CH CH2CHzCH2CH2 OH OH OH OH CH3 CH2CH CH2CH CH3 CH3 CH2CH CH2CH2CH2 945 a The two alkenes are lpentene and 2pentene Actually there are three alkenes since both the cis and trans isomers of 2pentene would work Here are their structures CH2CH CHzCHzCH3 CH3 CH CH CHzCH3 I pentene 2pentene b The best choice would be lpentene According to Markovnikov s Rule the hydration of lpentene would produce 2pentanol with only a trace of lpentanol If you used 2pentene you would get roughly equal amounts of 2pentanol and 3pentanol 947 There are many possible answers for each part of this question I ll give two examples for each part OH OH a CH3 CH2 and CH3 CH2 CH CH2CH3 OH OH b CH3 CH2 CH CH3 and CH3 CH CH 0 CH3CHzC CHzCHzCH3 and CHz CH3 CH3 CH3 OH d CH3 OH and CH2 949 Ethanol molecules can form hydrogen bonds with one another because they contain an 707H group Molecules of dimethyl ether in contrast cannot form hydrogen bonds with one another because they do not contain a hydrogen atom that is directly bonded to oxygen Therefore the attraction between ethanol molecules is much stronger than the attraction between dimethyl ether molecules giVing ethanol a much higher boiling point 951 953 955 Ethylene glycol has a very high tendency to form hydrogen bonds The attraction between ethylene glycol molecules is so strong that hexane molecules which cannot form hydrogen bonds are forced out of the area between the ethylene glycol molecules This is analogous to the reason that water will not mix with hexane Ethanol has a lower tendency to form hydrogen bonds so hexane molecules are not forced out of the area between ethanol molecules As a result ethanol and hexane mix with one another 957 You need 64 g of ethanol the calculator answer is 644952 g The isotonic concentration is 028 M so we need to use enough ethanol to make a 028 M solution First calculate the number of moles of ethanol in 500 mL ofthis solution 0 14 moles Then use the formula weight of ethanol 46068 to convert moles to grams 959 You make 14 g of ethanol the calculator answer is 139590047 g The molecular formula of ethene is C2H4 and the molecular formula of ethanol is C2H50 The balanced equation for the hydration reaction is C2H4 H20 gt C2H50 The formula weights of ethene and ethanol are 28052 and 46068 respectively so we get 46068 g of ethanol when we start with 28052 g of ethene Using this relationship as a conversion factor gives you the final answer 961 a The molecular formula of 2butanol is C4H100 and the formula weight is 7412 so one mole of 2butanol weighs 7412 g Therefore two moles weighs 14824 g b The volume is 185 mL the calculator answer is 184 837905 mL From part a you know that the mass is 14824 g Use the density as a conversion factor to convert grams into milliliters you need to turn the density upside down 963 a You need 4 g ofisopropyl alcohol b You need 18 g of isopropyl alcohol the calculator answer is 180282 g The molecular formula of isopropyl alcohol 2propanol is C3H80 so the formula weight is 60094 Therefore one mole of isopropyl alcohol weighs 60094 g Use this the volume of the solution and the molarity to calculate the mass of isopropyl alcohol Review molarity in Chapter 5 if you have forgotten how to do this 965 C2H50 3 02 gt 2C0 3 H20 967 Sodium ion is positively charged so it will be attracted to the negativelycharged oxygen atoms in the surrounding methanol molecules HO CH3 H CH3 0 0 CH3 H o H CH3
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