Let's break down each question step by step so you understand **carbon-13 NMR** and **DEPT** experiments! --- # 1. **How many signals would each molecule make in a carbon-13 spectrum?** - **Each unique carbon environment = 1 signal.** Look for symmetry! ### a. Ethyl methyl ether (CH₃CH₂OCH₃) - CH₃–CH₂–O–CH₃ - CH₃ (methyl group by O): 1 type - CH₂ (next to O): 1 type - CH₃ (ethyl group): 1 type **Total: 3 signals** ### b. 2-Butanone (CH₃COCH₂CH₃) - CH₃–CO–CH₂–CH₃ - CH₃ (by C=O): 1 type - CO (carbonyl): 1 type - CH₂: 1 type - CH₃ (at end): 1 type **Total: 4 signals** ### c. Benzene (C₆H₆) - All carbons are equivalent by symmetry. **Total: 1 signal** ### d. Cyclohexane (C₆H₁₂) - All carbons are equivalent by symmetry. **Total: 1 signal** ### e. Isopropyl chloride (CH₃)₂CHCl - (CH₃)₂CH–Cl - Two equivalent CH₃ groups: 1 type - Central carbon (attached to Cl): 1 type **Total: 2 signals** --- # 2. **Approximate chemical shift of each carbon atom** General ranges: - Methyl (CH₃): 10–20 ppm - Methylenes (CH₂): 20–40 ppm - Carbonyl (C=O): 180–220 ppm (ketones), 160–180 ppm (esters) - Aromatic: 120–140 ppm - Ether (C–O): 50–80 ppm - Alkyl-Cl: 30–50 ppm ### a. Ethyl methyl ether - CH₃ (by O): ~55 ppm - CH₂ (by O): ~65 ppm - CH₃ (ethyl): ~15 ppm ### b. 2-Butanone - CH₃ (by C=O): ~30 ppm - CO: ~205 ppm - CH₂: ~40 ppm - CH₃ (alkyl): ~15 ppm ### c. Benzene - Aromatic C: ~128 ppm ### d. Cyclohexane - All: ~26 ppm ### e. Isopropyl chloride - CH₃: ~23 ppm - CH (by Cl): ~48 ppm --- # 3. **Which carbon atoms will produce a peak in a DEPT-90 NMR experiment?** - **DEPT-90:** Only CH (methine) carbons show up. ### a. Ethyl methyl ether - None (no CH) ### b. 2-Butanone - CH₂, CH₃, and C=O (no CH) ### c. Benzene - Each C–H is a CH! - All 6 carbons show up. ### d. Cyclohexane - All are CH₂, so **none** show up. ### e. Isopropyl chloride - Central CH (attached to Cl): **shows up** --- # 4. **Which carbon atoms will produce a down peak in a DEPT-135 NMR experiment?** - **DEPT-135:** CH₃ and CH = positive (up), CH₂ = negative (down), quaternary and C=O = no peak. ### a. Ethyl methyl ether - CH₂ next to O: **down** ### b. 2-Butanone - CH₂: **down** ### c. Benzene - All CH (up) ### d. Cyclohexane - All CH₂: **down** ### e. Isopropyl chloride - No CH₂, so **none** --- # 5. **Assign each peak to a carbon atom in 2-butanone (from DEPT and C-13 spectrum)** - **Peaks at:** ~205, ~50, ~30, ~20 ppm - **DEPT-90:** Only one peak is "up" (so one CH) - **DEPT-135:** One "down" (CH₂), one "up" (CH₃), two "no" (quaternary or C=O) Assignment: - ~205 ppm: C=O (no DEPT) - ~50 ppm: CH₂ (down in DEPT-135) - ~30 ppm: CH₃ (up in DEPT-135) - ~20 ppm: CH₃ (up in DEPT-135) But 2-butanone only has one CH₂ and two CH₃ groups, but those two CH₃ are not equivalent. So, roughly: - 205: C=O - 50: CH₂ (next to C=O) - 30: CH₃ (next to C=O) - 20: CH₃ (end of chain) --- # 6. **Assign each peak in the ester (ethyl acetate) to a carbon atom** - **Peaks at:** ~170, 60, 20, 14 ppm - **DEPT-90:** Only one up (CH) - **DEPT-135:** One down (CH₂), two up (CH₃), one no (quaternary/C=O) Assignment: - 170: C=O (no DEPT) - 60: CH₂ (down in DEPT-135) - 20: CH₃ (up in DEPT-135, likely CH₃–CO) - 14: CH₃ (up in DEPT-135, likely CH₃–CH₂–O) --- ## **Summary Table** | Carbon Type | C-13 | DEPT-90 | DEPT-135 | |-------------|------|---------|----------| | CH₃ | Yes | No | Up | | CH₂ | Yes | No | Down | | CH | Yes | Up | Up | | C (quaternary/C=O) | Yes | No | No | --- If you need clarification on a specific molecule, let me know!