R and S denote the relative orientation of groups bound to a chiral carbon. Each bound group is relatively prioritized by their atomic components. Larger elements adjacent to a chiral carbon are given priority over less massive species. If two adjacent bonds are identical, subsequent atoms or bonds in those chains are considered until the tie is broken.

Once substituents are ordered, the absolute configuration may be determined by orienting the lowest priority substituent away from the point of observation. A circular path is made starting from the highest priority group towards the substituent of second highest priority, and around to the remaining group of yet lower priority. If the path proceeds clockwise, the absolute configuration is "R" and if it proceeds counter-clockwise, the absolute configuration is denoted "S".

At carbon 3, the oxygen of the hydroxy group is given highest priority, followed by the six-carbon chain extending to the left, then the two-carbon chain, and the bound hydrogen is given lowest priority.

At carbon 6, the five-carbon chain extending to the right is given highest priority, followed by the three-carbon chain, the deuterium, and the hydrogen is given the lowest priority.

In both instances, the hydrogen is already oriented away from the point of observation. Drawing paths from high priority to low, it is determined that both carbon 3 and carbon 6 are of the S configuration.

Always remember, like dissolves like. In this case, we have cyclopentane. Cyclopentane is simply a cyclic five-carbon chain, and is therefore extremely non-polar. Although  contains polar bonds, it is also a non-polar compound and can dissolve cyclopentane due to its tetrahedral shape. The four polar bonds all pull in equal and opposite directions, yielding a net of zero polarity on the compound. All other answer choices are polar compounds and would thus be better suited to solvate polar compounds.

 is the chemical formula for benzene and is the most stable out of the answer choices because it is the only listed molecule that is aromatic.

In most cases, negatively charged compounds are ranked as more basic, while positively charged compounds are deemed as more acidic. If two compounds have the same charge, we begin to look at the sze of the atom, then stabilization provided by resonance, then dipole induction.

The compound with the lowest  is always the most acidic. In this case, the electronegativity difference between hydrogen and chlorine is very large, and so the proton can dissociate very easily. This is why refer to  is a strong acid. Note that  is the only strong acid that is given as an answer choice.

Because of the visible attachments on the nitrogen, we might initially think that  assumes a trigonal planar shape, and is therefore planar. However, because there is no formal charge on , we know that there must be a lone pair present on the nitrogen atom. The lone pair can be thought of as another attachment, and so the  assumes a tetrahedral shape instead. Tetrahedrals are non-planar.

This nitrogen can be thought of as having 4 attachments: one carbon, two hydrogens, and one lone pair. The nitrogen assumes a tetrahedral shape and is sp³ hybridized.

When discussing solubility, remember the phrase, "like dissolves like."

Hexane, being made of solely carbons and hydrogens, is extremely nonpolar. Thus, our correct answer must also be nonpolar, as like dissolves like. Although carbon tetrachloride is made up of four polar bonds, the net charge on the molecule is zero, as the polar bonds all pull in equal and opposite directions. All other answer choices are polar, and thus insoluble in hexane.

We can answer this question simply by glancing at the periodic table. As a general trend, elements are more electronegative the more we move up to the "north-east" corner (stopping at fluorine), with fluorine being the most electronegative atom. Of the provided answer choices, oxygen is the most electronegative.

We can solve this problem using process of elimination. Right away, we can eliminate answer choice 2, as it is the only molecule that is not conjugated (increased conjugation leads to increased stability). Next, we can rule out answer choice 3, as it is less conjugated than the other two remaining options. Finally, we can arrive at answer choice 4 as our correct answer, because not only is this molecule the most conjugated, it is also aromatic. Aromatic molecules are highly stable. Recall that aromatic compounds follow the Huckel rule of pi electrons: 4n +2.