Organic Concepts - Organic Chemistry

A good nucleophile should not be bulky. If the nucleophile is bulky, the compound will not be able to reach the carbonyl carbon, where the reaction occurs. With increased steric hindrance due to a bulkier nucleophile, the reaction will run slowly, and the compound is not a good nucleophile. Good nucleophiles also want to give away electrons so that the reaction can occur. This means that conjugate bases make better nucleophiles than acids.

The side of the reaction that is favored will have the acid with the higher , because the reaction goes (strong acid + strong base weak acid + weak base).

Addition reactions involve breaking one pi bond (double bond) and forming two sigma bonds in the product.

E1 reactions occur in two steps, forming a carbocation intermediate, which is most stable if there is a protic solvent present. Furthermore, the use of a weak base favors E1.

E2 reactions occur in one step; thus no carbocation intermediate is formed, and an aprotic solvent is favored. E2 reactions are favored by strong bases and higher temperatures.

An elimination reaction occurs when there is a release of atoms in a given compound to produce two or more products. In the reaction given a hydrogen and chloride atom are eliminated from the original compound to form one 2-butene, potassium chloride and water molecule.

Heterolytic bond breaking occurs in polar compounds to form to products of opposite charges. In these types of reaction two electrons from the original bond stays with one fragment upon cleavage. In the reaction given, the bond between the hydrogen and chlorine atom is broken with the two electrons from the original bond staying with the chlorine atom. The resulting products are hydrogen ion and chloride ion.

Homolytic bond breaking occurs when a molecule breaks up to form two or more new products. In the reaction given, molecular chlorine forms two radicals in which one electron stays with each fragment formed.

All of the given answers reflect SN1 reactions, except the claim that SN1 reactions are favored by weak nucleophiles.

SN1 reactions occur in two steps and involve a carbocation intermediate. The product demonstrates inverted stereochemistry (no racemic mixture). Tertiary substrates are preferred in this mechanism because they provide stabilization of the carbocation.

SN2 reaction mechanisms are favored by methyl/primary substrates because of reduced steric hindrance. No carbocation is formed via an SN2 mechanism since the mechanism is concerted; thus a strong nuclephile is used.

Substitution reactions—regardless of the mechanism—involve breaking one sigma bond, and forming another sigma bond (to another group).

This reaction would use an SN1 mechanism because the leaving group, bromine, is on a tertiary carbon, which is a carbon attached to three other carbon atoms. The bulk of these methyl groups would make SN2 impossible, but it would make the carbocation produced by an SN1 reaction very stable. The methyl group would lead to hyperconjugation, which is a type of resonance that stabilizes transition states.

This reaction would occur using an SN1 mechanism because the leaving group is attached to a tertiary carbon, a carbon atom with three of the carbon atoms attached to it. The rate laws for SN1 mechanisms do not depend on the nucleophile concentration. The slow-step occurs unimolecularly within the molecule with the leaving group.

This question tests ones knowledge of carboxylic acid derivatives and how different groups effect reactivity. The order is 3, 1, 4, 2 and this is because of the electronic effect. Acid chloride (3) is first because of its electron withdrawing group making it most reactive. (1) is a weakly donating group and (4) is a normal strength donating group and (2) is a good electron donating group.

is the correct answer because it is the most conjugated molecule. is conjugated, but it is less conjugated than and is therefore less stable. Neither octane nor butene are conjugated.

A hydrocarbon is an alkene when it contains at least one carbon-carbon double bond. The double bond takes the place of two hydrogen atoms, and so the formula of an alkene involves two hydrogens less than an alkane.

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.

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.

By definition, a saturated hydrocarbon is a compound that contains no double or triple bonds-all single bonds. Of these choices, propane (-ane suffix indicates that it is an alkane, which contains only single bonds) is the only saturated hydrocarbon.

Hexane is a hydrocarbon consisting of 6 carbon atoms and 12 hydrogen atoms, making it nonpolar. Because it has no donatable hydrogen ions, it is also considered aprotic.