Organic Chemistry Flashcards
- Which of the following statements about carbon is NOT correct?
A. Carbon forms strong covalent bonds to itself, allowing chains and rings to be made.
B. Carbon expands its valence shell to accommodate more than eight electrons and thus forms double and triple bonds.
C. Carbon and hydrogen have similar electronegativity and form strong bonds to each other, thus avoiding the high reactivity shown by metal hydrides.
D. Carbon forms strong covalent bonds to elements like nitrogen and oxygen because it does not have lone pairs of valence electrons to destabilize the bonds.
B. Carbon expands its valence shell to accommodate more than eight electrons and thus forms double and triple bonds.
Which statement about bonding is TRUE?
A. A π bond is as twice as strong as a σ bond
B. A double bond consists of two π bonds
C. A σ bond has cylindrical symmetry about the bonding axis.
D. A π bond results from the sideways overlap of hybridized orbitals.
C. A σ bond has cylindrical symmetry about the bonding axis.
How many σ and π bonds are in acetylene?
A. 2σ, 2π
B. 3σ , 2π
C. 2σ, 3π
D. 3σ, 3π
B. 3σ , 2π
What is the bond angle and molecular geometry around C in CH2=CH2?
A. 120°, tetrahedral
B. 109.5°, tetrahedral
C. 120°, planar
D. 109.5°, planar
C. 120°, planar
What is the hybridization of O in CH3OH?
A. sp3
B. sp2
C. sp
D. sp3d
A. sp3
Oxygen in methanol has two lone pairs and forms two sigma bonds (one with hydrogen and one with carbon), making it have a tetrahedral electron geometry, which corresponds to sp³ hybridization.
Which of the following orbitals provide the most efficient overlap?
A. s-s
B. sp3 - sp3
C. sp-sp
D. p-p
C. sp-sp
How many constitutional isomers are possible for the molecular formula C5H12?
A. 1
B. 2
C. 3
D. 4
C. 3
How many distinct branched alkanes are there with the formula C6H14?
A. 1
B. 2
C. 3
D. 4
D. 4
Which of the following is TRUE for an optically active compound?
A. The molecular configuration is chiral.
B. The molecular configuration is achiral.
C. The compound is a racemic mixture of enantiomers.
D. The molecular configuration must have two or more stereogenic centers.
A. The molecular configuration is chiral.
Compounds which have different arrangements of atoms in space while having the same atoms bonded to each other are
A. constitutional isomers
B. functional group isomers
C. coordination isomers
D. Stereoisomers
D. Stereoisomers
Which of the following statements describes enantiomers?
A. They are achiral stereoisomers.
B. They are stereoisomers having a mirror plane of symmetry.
C. They are stereoisomers having non-identical mirror image configurations.
D. They are stereoisomers that do not have non-identical mirror image configurations.
C. They are stereoisomers having non-identical mirror image configurations.
Which substance can exist in enantiomeric forms?
A. 3-methylpentane
B. 2-methylpentane
C. 3-methyl-1-butanol
D. 2-methyl-1-butanol
D. 2-methyl-1-butanol
A racemic mixture consists of equal quantities of
A. cis-trans isomers
B. diastereomers
C. enantiomers
D. structural isomers
C. enantiomers
Which of the following is NOT an addition reaction?
A. Hydration
B. Dehydration
C. Halogenation
D. Hydrohalogenation
B. Dehydration
In this type of reaction, one sigma bond breaks and another forms at the same carbon atom.
A. Addition
B. Elimination
C. Substitution
D. Rearrangement
C. Substitution
In a substitution reaction, one sigma bond breaks and another sigma bond forms at the same carbon atom. This involves replacing one atom or group in the molecule with another, typically resulting in the same carbon atom being bonded to different groups.
During symmetrical bond breaking, ____ are formed.
A. Radicals
B. Electrophiles
C. Nucleophiles
D. None of the above
A. Radicals
All of the following are electrophiles EXCEPT
A. Br
B. BF3
C. AICI3
D. NH3
D. NH3
Br (Bromine): This can act as an electrophile, especially in reactions where it forms a positive ion (Br⁺).
BF₃ (Boron trifluoride): This is a strong electrophile due to the electron deficiency of boron, which has only six electrons in its valence shell.
AlCl₃ (Aluminum chloride): This is also a strong electrophile, particularly in Lewis acid-base reactions, as it can accept electron pairs.
NH₃ (Ammonia): Ammonia is a nucleophile because it has a lone pair of electrons on the nitrogen atom, allowing it to donate electrons rather than accept them.
Which of the following statements is FALSE?
A. It is not necessary for a nucleophile to have an unshared electron pair.
B. A species can react as an electrophile if it contains an atom (other than hydrogen) with an incomplete valence octet.
C. A species can react as an electrophile, even if it has one or more unshared electron pairs.
D. Any species bearing a lone pair can normally react as a nucleophile.
A. It is not necessary for a nucleophile to have an unshared electron pair.
Liquified petroleum gas is mainly composed of
A. Methane and Ethane
B. Ethane and Propane
C. Propane and Butane
D. Butane and Hexane
C. Propane and Butane
The hydrocarbon having the lowest boiling point is
A. CH4
B. C2H4
C. C4H10
D. C6H6
A. CH4
Compared to ionic compounds of similar molar mass, hydrocarbons typically have
I. Higher water solubility II. Higher melting points
A. I only
B. II only
C. both I and II
D. neither I nor II
D. neither I nor II
Which class of compounds consist exclusively of saturated hydrocarbons?
A. Alkenes
B. Aromatics
C. Alkynes
D. Alkanes
D. Alkanes
Alkanes undergo halogenation via
A. free radical substitution
B. electrophilic substitution
C. electrophilic addition
D. nucleophilic addition
A. free radical substitution
Alkenes and alkynes, because they contain π bonds, undergo this type of reaction.
A. Electrophilic addition
B. Nucleophilic addition
C. Electrophilic substitution
D. Nucleophilic substitution
A. Electrophilic addition
Alkenes and alkynes, due to their π bonds, undergo electrophilic addition reactions. The π electrons in these compounds are electron-rich and can be attacked by electrophiles, leading to the addition of atoms or groups across the double or triple bond. This type of reaction breaks the π bond and forms new σ bonds.
Which of the following reactions can reduce an alkene yielding an alkane?
A. Oxidation
B. Bromination
C. Hydrogenation
D. Polymerization
C. Hydrogenation
All of the following reactions convert alkenes to alcohols EXCEPT
A. halohydrin formation
B. ozonolysis
C. hydroboration-oxidation
D. oxymercuration-demercuration
B. ozonolysis
What is the position of the bromine atom relative to the methyl group in 3-bromotoluene?
A meta
B. para
C. ortho
D. trans
A meta
Aromatic compounds undergo substitution reactions instead of addition reactions because
A. the benzene ring is electron rich.
B. the hydrogens of benzene are relatively loosely bound.
C. the benzene ring is sterically crowded hence only substitution can occur.
D. the integrity of the benzene ring and the stable aromatic π system remains intact.
D. the integrity of the benzene ring and the stable aromatic π system remains intact.
Aromatic compounds, like benzene, undergo substitution reactions (such as electrophilic aromatic substitution) because these reactions allow the aromatic stability (the delocalized π system) to remain intact. Addition reactions would disrupt the conjugated π system and break the aromaticity, which is energetically unfavorable. Therefore, substitution reactions are preferred as they maintain the stability of the aromatic ring.
Which of the following substituents is NOT an ortho, para directing group in EAS?
A. -CI
B. -OH
C. -NO2
D. -CH3
C. -NO2
AlCl3 is a catalyst used in the alkylation and acylation of aromatic compounds. It is a(an)
A. Arrhenius acid
B. Brønsted-Lowry acid
C. Lewis acid
D. Lewis base
C. Lewis acid
AlCl₃ acts as a Lewis acid because it can accept a pair of electrons. In alkylation and acylation reactions (such as the Friedel-Crafts reactions), AlCl₃ accepts an electron pair from the halogen in an alkyl or acyl chloride, facilitating the formation of a carbocation or acylium ion, which then reacts with the aromatic compound.
Which of the following is arranged in order of increasing boiling point?
A. 2-methylbutane < n-pentane < butanone < butanol
B. n-pentane <2-methylbutane < butanone < butanol
C. 2-methylbutane < n-pentane < butanol < butanone
D. n-pentane < 2-methylbutane < butanol < butanone
A. 2-methylbutane < n-pentane < butanone < butanol
Methanal is used as
A. fuel
B. antiseptic
C. preservative
D. refrigerant
C. preservative
The simplest ketone is
A. acetone
B. lactone
C. cyclohexanone
D. ethyl methyl ketone
A. acetone
Carbonyl compounds undergo this type of reaction.
A. Electrophilic addition
B. Nucleophilic addition
C. Electrophilic substitution
D. Nucleophilic substitution
B. Nucleophilic addition
Carbonyl compounds, such as aldehydes and ketones, typically undergo nucleophilic addition reactions due to the electrophilic nature of the carbon atom in the carbonyl group (C=O). This makes them susceptible to attack by nucleophiles.
Ketones react with reducing agents to form
A. phenols
B. primary alcohols
C. secondary alcohols
D. tertiary alcohols
C. secondary alcohols
Ketones react with reducing agents (like NaBH₄ or LiAlH₄) to form secondary alcohols. The reduction process adds hydrogen to the carbonyl group (C=O) of the ketone, converting it into a hydroxyl group (-OH) attached to a carbon that is connected to two other carbon atoms, forming a secondary alcohol.
Which of the following will have the highest boiling point?
A. butane (58 g/mol)
B. propanal (58 g/mol)
C. 1-butanol (60 g/mol)
D. acetic acid (60 g/mol)
D. acetic acid (60 g/mol)
Carboxylic acids are more acidic than alcohols because
A. of the increased polarity of the O-H due to the carbonyl group.
B. of the stability of the carboxylate anion formed upon ionization.
C. of the higher K, value.
D. All of the above
D. All of the above
Which alkyl halide will most likely react via SN2 mechanism?
A. bromobenzene
B. bromomethane
C. 2-bromo-2-methylpropane
D. 1-bromobutane
B. bromomethane
Which chloroalkane undergoes substitution with OH- exclusively by an SN1 mechanism?
A. (CH3)3CCI
B. (CH3)2CHCH2CI
C. CH3CH2CHCICH3
D. CH3CH2CH2CH2CI
A. (CH3)3CCI
Among the following group of compounds, which will have the highest boiling point?
A. alkenes
B. alkynes
C. alcohols
D. haloalkanes
C. alcohols
An industrial source of alcohol.
A. coal
B. fats
C. sugar
D. ether
C. sugar
Which of the following will react faster with HBr?
A. 1-butanol
B. 2-butanol
C. 2-methyl-1-propanol
D. 2-methyl-2-propanol
D. 2-methyl-2-propanol
2-methyl-2-propanol (tert-butanol) will react faster with HBr because it forms a tertiary carbocation upon the loss of its hydroxyl group, which is more stable compared to primary or secondary carbocations. This stability leads to a faster reaction rate in the formation of alkyl halides via an SN1 mechanism. Tertiary alcohols generally react faster than secondary and primary alcohols with HBr.
Dehydration of an alcohol yields a(an).
A. alkene
B. alkyne
C. aldehyde
D. ketone
A. alkene
Dehydration of an Alcohol: This process involves the removal of a water molecule (H₂O) from an alcohol, typically under heat and in the presence of an acid catalyst.
The elimination of water results in the formation of a double bond, converting the alcohol into an alkene.
Which of the following can react with NaOH?
A phenol
B. ethanol
C. ethylene
D. diethyl ether
A phenol
Phenol can react with NaOH because it is acidic enough to donate a proton (H⁺) to form phenoxide ion (C₆H₅O⁻) and water. Ethanol, ethylene, and diethyl ether are not acidic enough to undergo this reaction with NaOH.
A compound having a permanent dipole moment is _____.
A. CO2 B. H2 C. CH4 D. CO
D. CO
CO is a polar molecule due to the difference in electronegativity between carbon and oxygen, leading to a permanent dipole moment. The other options (A. CO2 (linear so ma cancel ra ang each other), B. H2, and C. CH4) are either nonpolar molecules or have symmetrical arrangements that cancel out any dipole moments.
Which element can take part in hydrogen bonding?
A. F B. O C. N D. all of them
D. all of them
Only dispersion forces are present in _____.
A. HF B. C6H6 C. CO D.C2H5OH
Only dispersion forces are present in B. C6H6 (benzene).
Benzene is a nonpolar molecule, and its interactions are primarily due to dispersion forces (London dispersion forces). The other options—HF (polar), CO (polar), and C2H5OH (ethanol, which has hydrogen bonding)—all exhibit stronger intermolecular forces beyond just dispersion.