Eight highly challenging organic chemistry questions, each followed by a detailed step-by-step solution
**Question 1:**
**Problem:** Propose a synthesis of 2,4,6-trinitrotoluene (TNT) from toluene as the starting material. Include all necessary reagents and reaction steps.
**Solution:**
Synthesizing TNT from toluene is a complex process involving multiple steps, including nitration and subsequent functional group manipulations. Here's a summary of the steps:
1. **Nitration of Toluene**: Nitrate toluene using a mixture of concentrated nitric and sulfuric acids to obtain 2,4-dinitrotoluene (2,4-DNT).
2. **Isolation and Purification**: Isolate and purify 2,4-DNT by recrystallization.
3. **Mononitration of 2,4-DNT**: Nitrate 2,4-DNT again to obtain 2,4,6-trinitrotoluene (TNT).
**Question 2:**
**Problem:** Propose a retrosynthetic analysis for the synthesis of ibuprofen, a common nonsteroidal anti-inflammatory drug (NSAID).
**Solution:**
A retrosynthetic analysis for ibuprofen would break down the complex molecule into simpler fragments. One possible retrosynthetic pathway is:
- Ibuprofen
- Retrosynthetic Steps:
1. Remove the carboxylic acid group.
2. Disconnect the isobutyl side chain.
3. Disconnect the aromatic ring from the remaining fragment.
**Question 3:**
**Problem:** Design a synthesis of cyclohexanone starting from cyclohexane. Include all necessary reagents and reaction steps.
**Solution:**
The synthesis of cyclohexanone from cyclohexane involves a multi-step oxidation process. Here's an outline:
1. **Conversion to Cyclohexyl Hydroperoxide (CHHP)**:
- React cyclohexane with oxygen and a catalytic amount of a radical initiator to form CHHP.
2. **Conversion of CHHP to Cyclohexanol**:
- Reduce CHHP to cyclohexanol using a reducing agent like NaBH4.
3. **Conversion of Cyclohexanol to Cyclohexanone**:
- Oxidize cyclohexanol to cyclohexanone using a mild oxidizing agent like Jones reagent (CrO3 in H2SO4).
**Question 4:**
**Problem:** Perform a retrosynthetic analysis for the synthesis of 2-amino-3-methylbutanoic acid.
**Solution:**
A retrosynthetic analysis for 2-amino-3-methylbutanoic acid would break down the molecule into simpler fragments. One possible retrosynthetic pathway is:
- 2-amino-3-methylbutanoic acid
- Retrosynthetic Steps:
1. Disconnect the amino group (-NH2).
2. Disconnect the carboxylic acid group (-COOH).
3. Disconnect the methyl group (-CH3).
**Question 5:**
**Problem:** Propose a synthesis of 2,3-dibromobutane from butene as the starting material. Include all necessary reagents and reaction steps.
**Solution:**
The synthesis of 2,3-dibromobutane from butene involves bromination and regioselectivity control. Here's a summary of the steps:
1. **Anti-Markovnikov Bromination**:
- React butene with Br2 in the presence of a peroxide initiator (e.g., H2O2) to achieve anti-Markovnikov addition, forming 2-bromobutane.
2. **Bromination at the Other Position**:
- React 2-bromobutane with Br2 to add another bromine atom at the 3-position, forming 2,3-dibromobutane.
**Question 6:**
**Problem:** Design a synthesis of benzoic acid starting from toluene. Include all necessary reagents and reaction steps.
**Solution:**
The synthesis of benzoic acid from toluene involves oxidation. Here's a summary of the steps:
1. **Oxidation to Benzaldehyde**:
- React toluene with an oxidizing agent like chromyl chloride (CrO2Cl2) to obtain benzaldehyde.
2. **Oxidation of Benzaldehyde to Benzoic Acid**:
- Further oxidize benzaldehyde, preferably with a milder oxidizing agent like KMnO4, to form benzoic acid.
**Question 7:**
**Problem:** Perform a retrosynthetic analysis for the synthesis of caffeine.
**Solution:**
A retrosynthetic analysis for caffeine would break down the complex molecule into simpler fragments. One possible retrosynthetic pathway is:
- Caffeine
- Retrosynthetic Steps:
1. Disconnect the two imidazole rings.
2. Disconnect the xanthine core from the remaining fragments.
**Question 8:**
**Problem:** Propose a synthesis of meso-tartaric acid from a suitable starting material. Include all necessary reagents and reaction steps.
**Solution:**
The synthesis of meso-tartaric acid involves a series of reactions to achieve stereochemistry control. Here's a summary of the steps:
1. **Diastereoselective Dihydroxylation**:
- React a suitable alkene (e.g., maleic acid) with a dihydroxylation reagent like OsO4/NMO to obtain a diol with anti addition.
2. **Cleavage of the Diol**:
- Cleave the diol using periodic acid (HIO4) to obtain meso-tartaric acid.
These challenging organic chemistry questions and solutions cover various advanced topics, including retrosynthetic analysis, complex multistep syntheses, and stereochemistry control. They are designed to challenge graduate and undergraduate students in organic chemistry.
