Quiz

QUIZ

1. What is the most basic chemical representation of an enol?

a. RCOOH b. RCHOH c. RCH2OH d. RO

Answer: b. The most basic chemical representation of an enol is RCHOH representing an alkane to which a double bond is added as well as an alcohol group on the alkene. The actual name is alkene alcohol, which has been shortened somewhat to “enol”. It can also be represented as RR’COH, in which there are two side chains on the carbon atom.

2. What is the closest molecule chemically to the enolate molecule?

a. Ketone b. Carboxylic acid anion c. Alkoxyl group anion d. RR’OO anion

Answer: c. The chemical representation of the enolate anion is the RCHO anion or RR’CO, which is similar to the RCH2O alkoxyl group, both of which have the property of being nucleophilic by virtue of having a negative charge on the oxygen molecule, although the enolate molecule is more nucleophilic than the alkoxyl side chain because of the connected double bond.

3. What type of molecule can be considered the least acidic?

a. Enol b. Carboxylic acid c. Alkane d. Alcohol

Answer: c. Each of these will have acidic properties to some degree; however, alkanes have a pKa of 50, which makes them highly unlikely to give up a hydrogen ion.

4. How many alpha hydrogens are there on 1,3-diketone (diacetone), which is a molecule that is CH3COCH2COCH3?

a. 3 b. 5 c. 6 d. 8

Answer: d. These are unique molecules that have 8 alpha carbons because all of the hydrogen atoms are associated with a carbon atom that is next to a carbonyl group. Each of these will be an alpha hydrogen that has an increased acidity compared to a typical hydrogen atom because of a possible resonance structure within the molecule.

5. In the basic alpha halogenation of ketones via the reaction of the enolate, what happens to the halogen ion that is left over after the reaction occurs?

a. It forms a di-halogen molecule again b. It binds with hydrogen to form a halogen halide c. It binds to the oxygen molecule on the halogenated ketone d. It forms a salt

Answer: d. The basic conditions require the “using up” of hydroxide ions in sodium or potassium hydroxide. The hydroxide ions participate in water formation and the halogen forms a halogenated salt solution as a byproduct.

6. What is not an end-product of the haloform reaction?

a. Aldehyde b. Carboxylate c. Tri-haloform d. Water

Answer: a. This is a reaction that starts with a methyl ketone and ends with a carboxylate, a tri-haloform, and water.

7. What type of reaction is the aldol reaction which takes an aldehyde and combines it to make a beta-hydroxyaldehyde?

a. Nucleophilic subtraction b. Electrophilic substitution c. Nucleophilic substitution d. Nucleophilic addition

Answer: d. This is a nucleophilic addition reaction in which two aldehydes combine to make a beta-hydroxyaldehyde molecule (adding one molecule to the next).

8. The aldol reaction specifically starts with what type of molecule as a reactant?

a. Aldehyde b. Carboxylate c. Ketone d. Alkyl halide

Answer: a. The aldol reaction combines two aldehyde molecules using an enolate as an intermediary molecule.

9. In an aldol reaction, there will be some things that drive the reaction to make an enal or an enone. Which is not one of these?

a. Acidic environment b. The addition of heat c. The presence of an alpha hydrogen d. A nonaqueous environment

Answer: a. The aldol reaction first makes a beta-hydroxy molecule that will become an enal or an enone in the presence of heat and in nonaqueous environments that take water out of the dehydration equation. The presence of an alpha hydrogen is a necessity; however, it is not driven forward in an acidic environment.

10. If an intramolecular aldol reaction takes place in a dicarbonyl compound, what is the minimum number of carbon atoms between the carbonyl groups to make a stable compound after that?

a. 2 b. 3 c. 4 d. 5

Answer: c. There can only be stability in a five to six-membered carbon ring if there are four or more carbon atoms between and not counting the two carbonyl carbons. This will leave behind a five-membered ring.