Chem 241 Fall 2008 Practice Problems For Chapters 1 4 Question 1 Nitrate NO3 is a common inorganic anion that you have encountered in general chemistry The structure of the nitrate anion is shown below O Overall charge 1 N O O a On the structure above draw in the nonbonding valence electrons for each atom b On the structure above provide formal charges for each atom that bears a formal charge c What is the hybridization state of the nitrogen atom d Draw two additional resonance structures for the nitrate anion e Draw a resonance structure for the nitrate anion that has a positive charge on one of the oxygen atoms it is OK if this is a duplicate structure from part d Is this a major or minor resonance form Provide two justifications for your answer f Although nitrate appears to have one N O double bond and two N O single bonds all three bonds are actually the same length Explain 1 Chem 241 Fall 2008 Question 2 Translate the following Newman projections into Lewis structures line structures are OK a H Me Me b Me CH3 H3C Cl H Et c H Et Me CH3 Me Me C2 H6 OH F Question 3 Translate the following compounds into staggered Newman projections a 1 2 dichloroethane c H2NNH2 b Question 4 The chemical structure for vitamin A a highly unsaturated hydrocarbon with one oxygen atom is shown below Use this structure to answer the following questions H3C CH3 CH3 CH3 OH CH3 Vitamin A a How many degrees of unsaturation are there in vitamin A b How many atoms are sp3 hybridized c How many atoms are sp2 hybridized d How many atoms are sp hybridized e Label each double bond in vitamin A as E Z or not applicable 2 Chem 241 Fall 2008 Question 5 For each compound below briefly describe why the structure is unstable or cannot exist a Me b c d H C C H 3 Chem 241 Fall 2008 Question 6 For the following pairs of compounds circle the molecule that is more stable a b c Question 7 Label each of the following molecules as chiral or achiral a CHFBrCl b CHF2Br c 2 methylheptane d 3 methylheptane e 4 methylheptane f cis 2 butene g trans 2 butene h cis 1 2 dimethylcyclobutane i trans 1 2 dimethylcyclobutane 4 Chem 241 Fall 2008 Question 8 Assign the stereochemistry R or S for each stereocenter in the following molecules No you do not have to fully name the compounds Cl a Me H Br O b HO OH H3C H Me H c Me F OH Me Question 9 The common non steroidal analgesic ibuprofen has the structure shown below CH3 OH O ibuprofen a How many degrees of unsaturation does ibuprofen have 5 Chem 241 Fall 2008 b Only the S enantiomer of ibuprofen helps relieve pain Draw the S enantiomer of ibuprofen Question 10 The following compound is a bit of an oddity Is it chiral or achiral How many stereocenters does it contain Does it have an internal mirror plane Does this change our rules for chirality at all Br F F Br 6