Let’s break down each part step-by-step: --- ## **a) Draw the expected \( ^1\mathrm{H} \) NMR spectrum of the given compound** **Structure Analysis:** - The compound is 4-(Chloromethoxy)propiophenone. Identify different types of protons: 1. **Aromatic protons (phenyl ring, para-substituted):** - 4 protons, split into two doublets due to symmetry 2. **Methylene next to carbonyl (Ph-CO-CH2-):** - 2 protons, singlet/triplet, deshielded 3. **Methylene next to O (Ph-O-CH2-CH2-Cl):** - 2 protons, next to O, deshielded 4. **Methylene next to Cl (-CH2-Cl):** - 2 protons, next to Cl, highly deshielded ### **Expected \( ^1\mathrm{H} \) NMR Peaks:** | Proton Type | Chemical Shift (ppm) | Integration | Splitting | |----------------------------------|---------------------|-------------|-----------------| | Aromatic (para, 2x2H) | 7.8-8.2 & 7.-7.4 | 2H + 2H | Both doublets | | CH2 next to CO (Ph-CO-CH2-) | 2.8-3.2 | 2H | Triplet | | CH2 next to O (Ph-O-CH2-) | 3.8-4.2 | 2H | Triplet | | CH2 next to Cl (-CH2-Cl) | 3.6-4. | 2H | Triplet/Multiplet| #### **Diagram (not to scale):** ``` 8.2 8. 7.4 7.2 4.2 4. 3.8 3.2 3. 2.8 (ppm) |____| |____| |____| |____| |____| Ar-H Ar-H O-CH2- Cl-CH2- CO-CH2- (2H, d) (2H, d) (2H, t) (2H, t) (2H, t) ``` --- ## **b) Using \( ^1\mathrm{H} \) NMR to distinguish between alkenes A and B** ### **Structures:** - **A:** 1-methylcyclohex-1-ene (alkene at position 1, methyl at position 1) - **B:** 1-methylcyclohex-2-ene (alkene at position 2, methyl at position 1) ### **Key Differences in \( ^1\mathrm{H} \) NMR:** **Alkene Protons:** - **A (exocyclic alkene):** The double bond is at the ring junction. The alkene proton signals (vinyl protons) will appear as singlets or simple multiplets around 4.7–5.7 ppm. - **B (internal alkene):** The alkene hydrogens are on the ring, typically appearing as multiplets around 5.2–5.8 ppm, but with more complex coupling. **Methyl Group:** - **A:** The methyl is attached to the double bond (allylic), will appear upfield (1.5–2. ppm), possibly as a singlet. - **B:** Methyl is allylic to the double bond, similar region, but the pattern may differ due to the ring position. #### **How NMR Distinguishes Them:** - **Count and splitting of alkene proton signals:** - **A:** Should show *two* vinyl protons (same carbon, exocyclic, singlet or doublet). - **B:** Should show *three* vinyl protons (internal double bond; more complex multiplets). #### **Summary Table:** | Compound | Alkene Protons (ppm) | Multiplicity | Methyl Protons (ppm) | |----------|----------------------|--------------|----------------------| | **A** | ~4.7–5.1 (2H, s) | Singlet | ~1.6 (3H, s) | | **B** | ~5.2–5.8 (2–3H, m) | Multiplet | ~1.6 (3H, s) | ### **Conclusion:** - **Use the number and multiplicity of alkene proton signals in the \( ^1\mathrm{H} \) NMR to distinguish A and B.** - A: Exocyclic alkene (fewer, simpler vinyl signals) - B: Internal alkene (more vinyl protons, more complex multiplet) --- ## **Final Answers (Summary):** ### **a) 1H NMR Spectrum:** - 2 doublets (aromatic, 2H each, 7.–8.2 ppm) - 3 triplets/multiplets (three -CH2- groups, 2H each, 2.8–4.2 ppm, deshielded based on proximity to O, Cl, C=O) ### **b) Use of \( ^1\mathrm{H} \) NMR:** - Analyze alkene region (4.7–5.8 ppm) - Compound A: Simpler (exocyclic) alkene signals (singlet or doublet) - Compound B: More complex (internal) alkene signals (multiplet) Let me know if you need the actual chemical shift values or a drawn spectrum!