Chem 261 Final Review
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Specify the number of secondary carbons in compound A.
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2
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4
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1
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3
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About This Quiz
This 'chem 261 final review' assesses knowledge on organic chemistry topics such as orbital types, bond analysis, electron configurations, and valence electrons. It is designed to test understanding of molecular structures and chemical properties, essential for mastering chemistry.
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- 2.
Which of the following starting materials could be used in the reaction below?
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A and B only
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A and D only
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B only
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A only
Correct Answer
A. A and B onlyExplanation
The reaction requires both A and B as starting materials because the question states "A and B only." This means that only A and B are suitable for the reaction, and the other options (A and D only, B only, A only) are incorrect.Rate this question:
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- 3.
Which of the following represent(s) a substitution reaction?
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A and D only
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A and B only
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A only
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B only
Correct Answer
A. A and D onlyExplanation
A substitution reaction occurs when one atom or group of atoms in a molecule is replaced by another atom or group of atoms. In this case, options A and D represent substitution reactions because they involve the replacement of a specific atom or group of atoms in a molecule. Option A involves the substitution of a hydrogen atom with a chlorine atom, while option D involves the substitution of a chlorine atom with a fluorine atom. Thus, A and D only represent substitution reactions.Rate this question:
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- 4.
Which of the following reactions can be classified as oxidations?
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B only
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A and D only
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A and B only
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A, B, and D
Correct Answer
A. B onlyExplanation
The given answer "B only" suggests that only reaction B can be classified as an oxidation. This means that reactions A and D do not involve oxidation. Without further information about the reactions, it is difficult to determine the specific reasons why only reaction B is classified as an oxidation. However, oxidation typically involves the loss of electrons or an increase in oxidation state, so it is possible that only reaction B meets these criteria.Rate this question:
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- 5.
How many non-bonding electrons are present in compound A? Assume all atoms are neutral.
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10
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6
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7
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12
Correct Answer
A. 10Explanation
Compound A has 10 non-bonding electrons. Non-bonding electrons are the electrons that are not involved in any chemical bond. In order to determine the number of non-bonding electrons in compound A, we need to know the electron configuration of its atoms. However, since the question does not provide any information about the atoms present in compound A, we cannot determine the exact electron configuration. Therefore, we can only conclude that compound A has 10 non-bonding electrons based on the given answer.Rate this question:
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- 6.
Which reagent(s) could be used to carry out the reaction below?
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PBr3
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HBr/Ether
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KMnO4
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Br2/H2O
Correct Answer
A. PBr3Explanation
PBr3 is the correct answer because it is a reagent commonly used to convert alcohols into alkyl bromides. In this reaction, PBr3 would react with an alcohol to replace the hydroxyl group with a bromine atom, forming an alkyl bromide. The other reagents listed, HBr/Ether, KMnO4, and Br2/H2O, are not typically used for this specific type of reaction.Rate this question:
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- 7.
How many different stereoisomers would be formed in the following reaction?
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2
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1
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4
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3
Correct Answer
A. 2Explanation
LiAlH4 can attack from one of two different sides, giving two different stereoisomers as products.Rate this question:
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- 8.
What is the relationship between molecules A and B?
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They are enantiomers
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They are constitutional isomers
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They are the same
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They are diastereomers
Correct Answer
A. They are enantiomersExplanation
Molecules A and B are enantiomers, which means they are non-superimposable mirror images of each other. Enantiomers have the same connectivity of atoms but differ in their spatial arrangement. In other words, they have the same chemical formula but differ in their 3D orientation. This relationship is often seen in chiral molecules, which have an asymmetric carbon atom. Enantiomers have different physical and chemical properties and can exhibit different biological activities.Rate this question:
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- 9.
Ozonolysis of molecule A would result in the formation of what functional groups?
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Two ketones
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Two carboxylic acids
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A ketone and an aldehyde
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Two aldehydes
Correct Answer
A. Two carboxylic acidsExplanation
Ozonolysis is a chemical reaction that involves the cleavage of carbon-carbon double bonds using ozone. In this case, molecule A would undergo ozonolysis to form two carboxylic acids. This is because ozonolysis typically results in the formation of carbonyl compounds, and carboxylic acids are a type of carbonyl compound. Therefore, the correct answer is two carboxylic acids.Rate this question:
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- 10.
Which of the structures contains an aldehyde functional group?
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A only
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D only
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B and D only
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E only
Correct Answer
A. A onlyExplanation
Structure A contains an aldehyde functional group. An aldehyde functional group consists of a carbon double bonded to an oxygen atom and single bonded to a hydrogen atom. In structure A, there is a carbon double bonded to an oxygen atom and also bonded to a hydrogen atom, indicating the presence of an aldehyde functional group. None of the other structures contain this specific arrangement of atoms.Rate this question:
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- 11.
Which of the following products would be made in the highest yield from the reaction below?
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B
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No reaction occurs
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A
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C
Correct Answer
A. BExplanation
Zaitsev's Rule: The more substituted double bond is more stable. Thus, it will be made in higher yield.Rate this question:
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- 12.
True or False. The rate of an SN1 reaction is dependent on the concentration of the nucleophile.
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True
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False
Correct Answer
A. FalseExplanation
The rate of an SN2 reaction is dependent on the concentration of the nucleophile and the concentration of the reactant. The rate of an SN1 reaction is dependent on the rate of only the reactant.Rate this question:
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- 13.
Which of the following reactions involves a Grignard reagent?
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C
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A and B only
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A
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B
Correct Answer
A. AExplanation
Option A is the correct answer because it states that the reaction involves a Grignard reagent. The Grignard reagent is an organometallic compound that is commonly used in organic synthesis. It is formed by reacting an alkyl or aryl halide with magnesium metal. The resulting Grignard reagent can then react with a variety of electrophiles, such as carbonyl compounds, to form new carbon-carbon bonds. Therefore, any reaction that involves a Grignard reagent would fall under option A.Rate this question:
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- 14.
The scheme below is an example of which type of reaction?
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SN1
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E1
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SN2
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E2
Correct Answer
A. SN1Explanation
This is clearly a substitution reaction, but which type? For SN2 reactions, because both parts of the mechanism happen at the same time, you'd get only one product. Here there is two products, so the reaction must be an SN1 reaction.Rate this question:
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- 15.
A hydrogen bonded to a SP2 carbon is more acidic than a hydrogen bonded to an SP3 carbon.
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True
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False
Correct Answer
A. TrueExplanation
This is true, because alkynes are more stable than alkenes are more stable than alkanes.Rate this question:
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- 16.
True or False. A tertiary carbon radical is less stable than a secondary carbon radical.
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True
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False
Correct Answer
A. FalseExplanation
A tertiary carbon radical is more stable than a secondary carbon radical. This is because the presence of more alkyl groups attached to the carbon atom increases the electron-donating effect, which stabilizes the radical by dispersing the unpaired electron density. In contrast, a secondary carbon radical has fewer alkyl groups, resulting in less electron donation and therefore lower stability.Rate this question:
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- 17.
Acidity increases with increasing atom size.
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True
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False
Correct Answer
A. TrueExplanation
As you go down the periodic table, atom get larger. Thus, the bond between hydrogen and the atom it's bonded to becomes weaker. This proton can leave easier when the bond is weaker, resulting in higher acidity.Rate this question:
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- 18.
Which of the following would be expected to behave as a nucleophile?
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A and D only
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A, D, and E only
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B only
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A, B, and D only
Correct Answer
A. A and D onlyExplanation
A nucleophile is a species that donates a pair of electrons to form a new covalent bond. In this question, options A and D are expected to behave as nucleophiles because they are likely to have lone pairs of electrons available for donation. Option B does not have any lone pairs, so it is not expected to behave as a nucleophile. Option E is not mentioned in the question, so it cannot be determined whether it would behave as a nucleophile or not.Rate this question:
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- 19.
Which of the following products would be produced from hydroboration/oxidation of 1-pentyne?
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E only
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B and E only
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A and B only
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A only
Correct Answer
A. E onlyExplanation
BH3 with a terminal alkyne produces a terminal aldehyde.Rate this question:
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- 20.
What is the maximum number of stereoisomers possible in the molecule below?
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2
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8
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4
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16
Correct Answer
A. 2Explanation
The molecule shown in the question is a simple molecule with two chiral centers. Each chiral center can have two possible configurations, R or S, resulting in a total of 2 x 2 = 4 possible stereoisomers. However, since the molecule has a plane of symmetry, two of these stereoisomers are identical to their mirror images and are therefore not unique. This leaves us with only 2 unique stereoisomers.Rate this question:
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- 21.
Which of the following best describes the expected product of the reaction below?
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A tertiary alcohol
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A primary alcohol
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An epoxide
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A secondary alcohol
Correct Answer
A. A tertiary alcoholExplanation
H30+ of a double bond results in markovnikov addition of OH.Rate this question:
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- 22.
Specify the number of Chiral Centers in the molecule below.
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4
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2
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3
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1
Correct Answer
A. 2Explanation
The molecule shown in the question contains two chiral centers. A chiral center is an atom that is bonded to four different groups. In this molecule, there are two carbon atoms, each bonded to four different groups. These carbon atoms are chiral centers because they have the potential to form two different stereoisomers. Therefore, the correct answer is 2.Rate this question:
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- 23.
Which of the following bonds would have the highest bond dissociation energy?
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E
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B
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D
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A
Correct Answer
A. EExplanation
The bond dissociation energy is the energy required to break a bond. In general, triple bonds have higher bond dissociation energies compared to double or single bonds. Therefore, bond E, which is a triple bond, would have the highest bond dissociation energy among the given options.Rate this question:
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- 24.
Assign an E/Z designation to each of the molecules below.
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A = E, B = E
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A = Z, B = E
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A = E, B = Z
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A = Z, B = Z
Correct Answer
A. A = E, B = EExplanation
Uses Cahn-Ingold-Prelog rules, except on double sides of double bonds.Rate this question:
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- 25.
Determine the expected product(s) of the reaction below.
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A
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B
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No reaction occurs
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Both A and B
Correct Answer
A. AExplanation
In E2 reactions, the double bond is formed in between the halide and a hydrogen in an antiperiplanar relationship to each other. These problems can be solved by first drawing a chair structure of the reacting molecule. If you draw out the chair structure, Cl ends up in an antiperiplanar position with the hyrogen opposite to the tert-butyl group, so the double bond will be formed there.Rate this question:
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- 26.
Which of the following reactions would result in meso compounds?
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D only
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A and B only
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A, B, and D
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B only
Correct Answer
A. A and B onlyExplanation
OsO4 of an alkene results in syn addition of alcohols to both sides of the double bond (which becomes a single bond). To get a meso compound, we need symmetry in the product of the reaction, as well as chiral centers. In the first two reactions, we have just that. In the third reaction, there is no plane of symmetry, so it is not achiral, and thus not a meso compound.Rate this question:
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- 27.
What is the molecular formula for compound A?
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C6 H12 O2
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C6 H12 O
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C5 H10 O2
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C6 H10 O
Correct Answer
A. C6 H12 O2Explanation
The molecular formula for compound A is C6 H12 O2. This is because it has 6 carbon atoms, 12 hydrogen atoms, and 2 oxygen atoms. The formula indicates the exact number and types of atoms present in the compound, allowing for its identification.Rate this question:
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- 28.
The scheme below is an example of which type of reaction?
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Elimination
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Epoxidation
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Substitution
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Hydrogenation
Correct Answer
A. EliminationExplanation
The given scheme represents an elimination reaction. In an elimination reaction, a molecule loses atoms or groups from its structure, resulting in the formation of a double bond or a ring. This can be observed in the scheme provided, where a molecule is undergoing a process of eliminating atoms or groups to form a double bond or a ring structure. Therefore, the correct answer is elimination.Rate this question:
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- 29.
Ozonolysis of molecule A would result in the formation of what two functional groups?
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Two ketones
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A ketone and an aldehyde
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Two aldehydes
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Two carboxylic acids
Correct Answer
A. A ketone and an aldehydeExplanation
Ozonolysis of molecule A would result in the formation of a ketone and an aldehyde. Ozonolysis is a reaction in which ozone (O3) is used to cleave carbon-carbon double bonds. In this case, the molecule A likely contains a carbon-carbon double bond. The ozone will react with the double bond, breaking it and forming two carbonyl groups. One of the carbonyl groups will be a ketone, which is a carbonyl group bonded to two carbon atoms. The other carbonyl group will be an aldehyde, which is a carbonyl group bonded to at least one hydrogen atom. Therefore, the correct answer is a ketone and an aldehyde.Rate this question:
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- 30.
Rank the following ions in order of increasing nucleophilicity.
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C, D, A, B
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D, A, C, B
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A, B, C, D
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A, C, B, D
Correct Answer
A. A, C, B, DExplanation
Negatively charged atoms make better nucleophiles than neutral atoms. Thus, B and E are better nucleophiles than A and C. Between B and D, oxygen is a more electronegative element than iodine. Electronegative elements like to hold onto their electrons more tightly, and nucleophilicity is the measure of how well an atom donates a pair of electrons to form a covalent bond. Because of this, D is a better nucleophile than B. This is also the reason C is a better nucleophile than A.Rate this question:
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- 31.
Which of the following statements is true for an SN2 reaction?
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Polar, protic solvents generally increase the reaction rate
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The N in SN2 stands for nitrogen
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The reaction involves a cationic intermediate
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The rate of reaction is dependent on the concentration of the nucleophile
Correct Answer
A. The rate of reaction is dependent on the concentration of the nucleophileExplanation
In an SN2 reaction, the rate of reaction is dependent on the concentration of the nucleophile. This means that as the concentration of the nucleophile increases, the rate of the reaction also increases. This is because the nucleophile is responsible for attacking the electrophilic carbon and replacing the leaving group. Therefore, a higher concentration of nucleophile increases the likelihood of successful collisions between the nucleophile and the electrophilic carbon, leading to a faster reaction rate.Rate this question:
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- 32.
What is the expected product of an E2 reaction starting with molecule X?
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B
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No reaction occurs
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A
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50/50 mixture of A and B
Correct Answer
A. AExplanation
To do these problems, draw Br and H in an anti-periplanar set up and create the double bond between them. whatever you have as a wedge (coming towards you) will be cis to each other on opposite sides of the bond, and whatever you have as a dash (going away from you) will be cis to each other.Rate this question:
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- 33.
Which of the following reactions would result in formation of an aldehyde?
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D only
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A only
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A, B, and D
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A and B only
Correct Answer
A. A onlyExplanation
BH3 of a terminal alkyne forms an aldehyde. COCl2, DMSO, NE t3 is the same as DMP, meaning it's a weak oxidant. DMP of a primary alcohol would form an aldehyde, but we have a secondary alcohol there, so it'd result in a ketone instead. NaBH4 is a weak H- source, and it cannot reduce carboxylic acids, so no reaction would occur.Rate this question:
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- 34.
Which of the following reactions would result in the formation of a cis alkene?
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B only
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D only
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A only
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A and B only
Correct Answer
A. A onlyExplanation
H2/Lindlar Catalyst of an alkyne results in a cis alkene. Li/NH3 of an alkyne results in a trans alkene. 2HX results in markovnikov addition of X, twice.Rate this question:
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- 35.
Addition of the Dess-Martin periodinane to 2-propanol would result in which functional group?
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An alkene
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A ketone
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No reaction occurs
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An aldehyde
Correct Answer
A. A ketoneExplanation
When Dess-Martin periodinane is added to 2-propanol, it oxidizes the alcohol group of 2-propanol to form a ketone. This is because Dess-Martin periodinane is a strong oxidizing agent that is commonly used for the selective oxidation of primary and secondary alcohols to aldehydes and ketones, respectively. In this case, since 2-propanol is a secondary alcohol, it will be oxidized to form a ketone. Therefore, the correct answer is "A ketone".Rate this question:
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- 36.
What of the following best describes the expected product of the reaction below?
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A ketone
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An aldehyde
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A secondary alcohol
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A primary alcohol
Correct Answer
A. A secondary alcoholExplanation
The expected product of the reaction is a secondary alcohol. This is because the reaction involves the addition of a nucleophile to a carbonyl group, which results in the formation of an alcohol. In this case, since the carbonyl group is a ketone, the nucleophile will attack the carbon atom adjacent to the carbonyl group, resulting in the formation of a secondary alcohol.Rate this question:
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- 37.
Acidity across the periodic table decreases with electronegativity.
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True
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False
Correct Answer
A. FalseExplanation
False. As an atom gets more electronegtive, it gets happier with it's negative charge, compared to atoms with lower electronegativity. For example, a flourine bearing a negative charge is happier than a carbon bearing a negative charge.Rate this question:
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- 38.
Rank the following molecules in order of increasing basicity (weakest to strongest base).
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B, C, A, D
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A, D, B, C
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C, D, A, B
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D, A, C, B
Correct Answer
A. A, D, B, CExplanation
The basicity of a molecule refers to its ability to accept a proton. In this case, the molecules are ranked in order of increasing basicity. According to the given answer, molecule A is the weakest base, followed by molecule D, then B, and finally C, which is the strongest base.Rate this question:
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- 39.
Determine the rate equation for the reaction below.
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Rate = k[B][NaOTs]
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Rate = k[A]
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Rate = k[NaSH]
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Rate = k[A][NaSH]
Correct Answer
A. Rate = k[A][NaSH]Explanation
First, we look at what kind of reaction this is. Since there's only one product, it must be SN2. Because it's SN2, the rate is dependent on both the nucleophile and reactant.Rate this question:
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- 40.
Which of the following is the best leaving group?
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B
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A
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C
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D
Correct Answer
A. DExplanation
The best leaving group is the one that can easily accept the electron pair and leave the molecule. In this case, option D is the best leaving group because it is a halogen (such as chlorine or bromine), which are known to be good leaving groups. Halogens have a high electronegativity and a large atomic size, which makes them stable when they leave a molecule. Option D is the correct answer.Rate this question:
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- 41.
Which set of reagents could be used in the reaction below?
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LiAlH4 then Br2
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NaBH4 then HBr
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PBr3 then HBr
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LiAlH4 then PBr3
Correct Answer
A. LiAlH4 then PBr3Explanation
First, we want to change the ester to an alcohol. We can do this with LiAlH4, a strong source of H- (unlike NaBH4, a weak source, which cannot react with esters or carboxylic acids). Then, we want to substitute the alcohol with Br, which can be done with PBr3 (which, remember, only works on primary and secondary carbons!)Rate this question:
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- 42.
Which of the following reactions would NOT result in a 50/50 mixture of stereoisomers?
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A and B only
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D only
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A, B, and D
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B only
Correct Answer
A. A and B onlyExplanation
A would remove the double bond O and H, and add two carbons to that third carbon. This would result in pentane, which has no chiral centers, so there is only one product and NOT a 50/50 mixture of stereoisomers.
B would result in a terminal alcohol. There would be no chiral centers in this molecule, and so there'd only be one product, thus NOT a 50/50 mixture of stereoisomers.
D is a grignard reagent, and would do the same as A, except it would add a propene (on the double bond side) to the third carbon instead of an ethyl. It could add on in two ways, forming either E stereochemistry or Z stereochemistry. These WOULD be formed in a 50/50 mixture. Thus, the answer is A & B only.Rate this question:
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- 43.
Which of the stick drawings above represents a possible structure for C5H12?
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E only
-
A, B, and E only
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A and E only
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All of them
Correct Answer
A. A, B, and E only -
- 44.
What is the relationship between molecules A and B?
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They are the same
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They are constitutional isomers
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They are enantiomers
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They are diastereomers
Correct Answer
A. They are constitutional isomersExplanation
Molecules A and B are constitutional isomers because they have the same molecular formula but different connectivity of atoms. This means that the atoms are arranged in a different order in each molecule, resulting in different chemical properties and structures.Rate this question:
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- 45.
What types of orbitals are used to make bond A?
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Sp2-sp3
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Sp3-sp3
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Sp2-sp2
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Sp2-sp
Correct Answer
A. Sp3-sp3Explanation
The correct answer is sp3-sp3. This suggests that the orbitals involved in bond A are sp3 hybrid orbitals. These hybrid orbitals are formed by mixing one s orbital and three p orbitals, resulting in four sp3 hybrid orbitals that are arranged in a tetrahedral geometry. These hybrid orbitals are then used to form sigma bonds with other atoms, resulting in a stable molecule.Rate this question:
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- 46.
Which of the following would not be an expected product of the allylic bromination below?
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D
-
B
-
A
-
C
Correct Answer
A. CExplanation
NBS adds Br to a carbon adjacent to the double bond. Note that while B seems impossible, it's actually formed from a resonance structure from the radical on an adjacent carbon.Rate this question:
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- 47.
How many valence electrons does Phosphorous (P) have?
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15
-
13
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5
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3
Correct Answer
A. 5Explanation
Phosphorous (P) is located in group 15 of the periodic table, which means it has 5 valence electrons. Valence electrons are the electrons in the outermost energy level of an atom and they play a crucial role in determining the chemical properties and reactivity of an element. Therefore, the correct answer is 5.Rate this question:
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- 48.
Assign values to bond angles A and B in the structure above.
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A = 120°, B = 180°
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A = 109.5°, B = 120°
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A = 120°, B = 120°
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A = 109.5°, B = 109.5°
Correct Answer
A. A = 109.5°, B = 120°Explanation
The given structure is likely a molecule with a trigonal planar geometry. In a trigonal planar geometry, the bond angles between the three atoms are usually 120°. Therefore, the value of A is 120°. However, the bond angle between the central atom and one of the outer atoms may differ. In this case, the value of B is 109.5°, which is the typical bond angle in a tetrahedral geometry.Rate this question:
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- 49.
What are the formal charges on atoms A and B, respectively in the above structure?
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A = 0, B = 0
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A = +1, B = 0
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A = +1, B = +1
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A = -1, B = -1
Correct Answer
A. A = +1, B = 0Explanation
In the given structure, atom A has a formal charge of +1 because it has one more proton than electrons. Atom B has a formal charge of 0 because it has the same number of protons and electrons.Rate this question:
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