Organic Chemistry 1 — Questions and Answers
Question 1: What is the functional group present in alcohols?
- Carboxyl
- Carbonyl
- Hydroxyl (Correct answer)
- Amino
Correct answer: Hydroxyl
Alcohols are organic compounds characterized by the presence of a hydroxyl functional group. This group consists of an oxygen atom bonded to a hydrogen atom (-OH), which is then attached to a carbon atom. The hydroxyl group is responsible for many of the characteristic properties of alcohols, including their ability to form hydrogen bonds and their polarity.
Question 2: What is the hybridization of the carbon atom in ethene (C2H4)?
- sp3
- sp
- sp2 (Correct answer)
- None of the above
Correct answer: sp2
In ethene (C2H4), each carbon atom is double-bonded to another carbon atom and single-bonded to two hydrogen atoms. This arrangement results in three electron domains around each carbon atom, leading to a trigonal planar geometry. To accommodate this, the carbon atoms undergo sp2 hybridization, where one s orbital and two p orbitals combine to form three sp2 hybrid orbitals.
Question 3: Which reagent is commonly used for the bromination of alkenes?
- HBr
- Br2 (Correct answer)
- NaBr
- KBr
Correct answer: Br2
Bromine (Br2) is the common reagent used for the bromination of alkenes, typically in a non-polar solvent like CCl4. This reaction is an electrophilic addition, where the double bond of the alkene acts as a nucleophile, attacking the bromine molecule. The result is the addition of two bromine atoms across the double bond, forming a vicinal dibromide.
Question 4: What type of reaction mechanism is followed in the substitution of a primary alkyl halide with a strong nucleophile?
- SN1
- E1
- SN2 (Correct answer)
- E2
Correct answer: SN2
The substitution of a primary alkyl halide with a strong nucleophile typically follows an SN2 (bimolecular nucleophilic substitution) reaction mechanism. In SN2 reactions, the nucleophile attacks the carbon atom bearing the leaving group from the backside, leading to a concerted bond-breaking and bond-forming process. Primary alkyl halides are favored for SN2 due to less steric hindrance around the electrophilic carbon.
Question 5: Which of the following is an example of an aromatic compound?
- Cyclohexane
- Benzene (Correct answer)
- Ethane
- Propane
Correct answer: Benzene
Benzene is the quintessential example of an aromatic compound. Aromatic compounds are cyclic, planar molecules with a continuous ring of p-orbitals containing a specific number of pi electrons (4n+2, according to Hückel's rule). Benzene fits this criteria with its six-membered ring and six pi electrons, exhibiting enhanced stability due to delocalization.
Question 6: What is the major product when propene reacts with HBr in the presence of peroxides?
- 2-bromopropane
- 1-bromopropane (Correct answer)
- 1,2-dibromopropane
- Propan-1-ol
Correct answer: 1-bromopropane
When propene reacts with HBr in the presence of peroxides, the reaction follows an anti-Markovnikov addition mechanism. Peroxides initiate a radical mechanism, causing the bromine atom to add to the less substituted carbon of the double bond, and the hydrogen atom to add to the more substituted carbon. This results in the formation of 1-bromopropane as the major product.
Organic Chemistry 1
What is the functional group present in alcohols?