The five resonance structures of the given molecule are shown below:

The nitro substituent is strongly deactivating, ketones are moderately deactivating substituent, halides are weakly deactivating, alkyl groups are weakly activating, and amine groups are strongly activating.

An SN1 mechanism involves the leaving of the bromine in the first step and the formation of a carbocation on that carbon. The molecule with the most stable carbocation will react most quickly.

The carbocation is most stable on the most highly substituted carbon. All the of the answer options form primary or secondary cations except for one. The correct answer has a carbocation on a carbon bonded to two methyl groups and one ethyl group. The correct answer is .

Grignard reagents attack ketones at the site of the ketone's carbon to produce tertiary alcohols.

SN2 reactions require a strong nucleophile. If the the nucleophile is weak, SN1 is favored over SN2.

For SN2 reactions less substitution in the electrophile is favored (methyl > primary > secondary).

For SN2 reactions polar aprotic solvents are preferred (DMSO, acetone, DMF and ethers are common polar aprotic solvents). Polar protic solvents (ethanol, methanol) favor SN1 reactions.

In this question, we're presented with a hypothetical reaction, and we're asked to identify which type of reaction is occurring. Let's go through each of the answer choices to see which one fits.

Addition reactions are ones in which two atoms or molecules come together. It takes the form of .

Elimination reactions are essentially the opposite of addition reactions. In this case, a molecule splits into two, taking the form of .

Rearrangement reactions are ones in which the reactant is manipulated in a way that gives product, but in the process, no additional reactants are consumed and no additional products are made. It takes the general form of .

Substitution reactions are ones in which there is some sort of exchange of atoms or functional groups between different reactants to give new products. In the reaction shown in the question stem, this qualifies as a substitution reaction.

Regarding chemical reactions, the activation energy is the minimum energy which must be available in a chemical system in order for reactants to participate in a chemical reaction. Catalysts speed up reactions by lowering this minimum energy. Raising it would have the opposite effect. Catalysts do not alter the  of a reaction. Remember this--it is a common error to make!

Most organic reactions are carried out in multiple steps. The rate equation can be derived from the process that occurs in the slowest step of the mechanism. An E1 reaction's slow step is when a leaving group separates from the hydrocarbon and a carbocation is formed. The only reactant in this step is one molar equivalent of the hydrocarbon. Thus, the rate equation only depends on that substance. The molar equivalent determines the exponent of each reactant in the equation.

By and large, organic compounds contain mainly covalent bonds. Covalent bonds are typically harder to break, which is why organic reactions happen at a relatively slower rate than inorganic reactions.

Neither lithium aluminum hydride, nor sodium borohydride will reduce C–C double bonds.

H₂/Raney nickel and H₂/Pd can each (individually) reduce an alkene to an alkane. Since both H₂/Raney nickel and H₂/Pd can reduce the alkene, the answer is both of those reagents. This is a catalytic hydrogenation reaction, and H₂/Raney nickel not only reduces C–C double bonds, but also carbonyl compounds.