Consider the Lewis structure for the polyatomic oxyanion shown below, where X is an element from the 3 rd period (Na-Ar). By changing the overall charge, n, from 1- to 2- to 3- we get three different polyatomic ions. For each of these ions, if the Lewis structure you drew in part (c) differs from the Lewis structure shown below, which one do you think is the best one (if you were able to choose only a single Lewis structure)?

Write structure for the compound shown below: (a) 1-bromo-3-methylbenzene.

Write structure for the compound shown below: (b) 1-chloro-2-propylbenzene.

Consider the chemical structure below. What are the formal charges of the atoms shown in red?

(a) Which of the compounds shown in mentioned figure can in principle be resolved into enantiomers? Explain why or why not. (b) Omeprazole can be separated into two enantiomers that do not interconvert at room temperature. What atom is the asymmetric center in omeprazole? (c) Esomeprazole, the $S$ enantiomer of omeprazole, is a drug used to control acid reflux. Redraw the structure of omeprazole in part (b) to show it as the $S$ enantiomer. (Hint: An unshared electron pair has lower priority than H.)

Draw the Lewis dot structure of NI$_3$.

The polymer whose structure is shown below is made from two different monomers. Identify the monomers.

How to draw a Lewis structure of NI${_3}$?

In which of the molecules below is the carbon-carbon distance the shortest?

A) $\ce{H2C=CH2}$

B) $\ce{H-C≡C-H}$

C) $\ce{H3C-CH3}$

D) $\ce{H2C=C=CH2}$

E) none of above

Use the $\delta$+/$\delta$- convention to indicate the direction of expected polarity for each of the bonds indicated. (a) H3C–Cl (b) H3C–NH2 (c) H2N–H (d) H3C–SH (e) H3C–MgBr (f) H3C–F

Classify each organic compound as a hydrocarbon or a functionalized hydrocarbon. For functionalized hydrocarbons, identify the compound's family.

a. $\ce{H3C-CH2OH}$

b. $\ce{H3C-CH3}$

c. $\ce{H3C-CO-CH2-CH3}$

d. $\ce{H3C-NH2}$

Cocaine is a widely abused, addicting drug. Cocaine is usually obtained as its hydrochloride salt (cocaine hydrochloride, an ionic salt). This salt can be converted to crack (a neutral molecule) by treatment with base.
a. Identify the functional groups in cocaine.
b. Given what you have learned about ionic and covalent bonding, which of the two compounds—crack or cocaine hydrochloride—has a higher boiling point?
c. Which compound is more soluble in water?
d. Can you use the relative solubility to explain why crack is usually smoked but cocaine hydrochloride is injected directly into the bloodstream?

The structure below is a pentose sugar and does not have stereochemistry specified.

Reduction of the aldehyde functional group results in the structure below. How many different stereoisomers exist for this structure?

Circle the functional groups in the following structures. State to which class (or classes) of compounds the structure belongs.