1. (9 pts) Write a valid Lewis structure for each of the following. Show lone pairs and formal charges where necessary. Draw covalent bonds as lines. (a) bisulfate ion, HSO4-
O HO S O
(b) hydrogen cyanide, HCN
(c) hydrazoic acid, HN3 (arranged HNNN)
2. (10 pts) Indicate which of the following pairs do not constitute resonance structures by drawing an “X” in the space provided?
O CH3C-O O
CH3C O OH
CH3C-OH O CH3CCH3
CH3C O OH CH3C CH2
X X X X
and and and
CH2CH CH 2 HOCN
CH2 CH CH2
3. (8 pts) What is the hybridization of the Carbon indicated in bold in the following compounds? H2C=O
4. (10 pts) Malonic acid, HO2CCH2CO2H, is a diprotic acid. The pKa for the loss of the first proton is 2.83; the pKa for the loss of the second proton is 5.69. (a) Explain why malonic acid is a stronger acid than acetic acid (pKa = 4.75). (b) Explain why the anion, -O2CCH2CO2H, is so much less acidic than malonic acid itself. (a) electron withdrawing –CO2H group stabilizes charge of conjugate anion (b) molecules doesn’t want to be dianion
5. (11 pts) Carey. All the parts of this problem refer to the alkane having the carbon skeleton shown.
(a) (2 pts) What is the molecular formula of this alkane? C13H38
(b) (2 pts) What is the IUPAC name? 5-ethyl-2,6-dimethylnonane 1 pt for or 1 pt for 5-ethyl-4,8-dimethylnonane 2,6-dimethyl,5-ethylnonane
(1 pt) How many methyl groups are present in this alkane?____5 (1 pt) How many methylene groups?______5______ (1 pt) How many methine groups?_________3___ (1 pt) How many carbons are primary?______5____ (1 pt) How many are secondary?_____5_______ (1 pt) How many are tertiary?________3___ (1 pt) How many are quaternary?______0______ 6. (8 pts) Carey. Female tiger moths signify their presence to male moths by giving off a sex attractant (pheromone). The sex attractant has been isolated and found to be a 2-methyl-branched alkane having a molecular weight of 254. What is this material?
(12 X 18) + 38 = 254
2-methylheptadecane also OK as is CH3(CH2)14CH(CH3)2 7. (6 pts). Write the products of the following reactions indicated by curly arrows.
H H BH2 BH2
H CH3 CH2
8. (14 pts) Carey. Write structural formulas for all the constitutional isomers have the give formulas. (a) C3H4
(b) C3H9N CH3CH2CH2NH2 CH3CH2NHCH3
CH3 H3C N CH3
9. (12 pts) Below are 9 structures of compounds with four atoms, one H, one C, one N, and one O. Lone pairs and formal charges have not been added. Circle the pairs that are resonance structures after elaboration of Lewis structures.
+ + + +
Resonance pairs are
10. Carey. (8 pts) Rank the following in order of decreasing acidity.
N H HO CH3 H
11. (4 pts) Carey. What are the formulas of the following:
O OCCH3 H N O
OCCH3 aspirin C10 H10O4 O O
N H indigo
C16 H10N2 O2