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Vibrational Spectrum Academic Peak Assignment Report
Report No.: jwh250_fresh_20260801_110149 · Date: 2026-08-02 12:49:53 · Prepared by: FTIR.fun spectral-audit skill (CLAUDE)
Sample Information
| Source file | 10___jwh-250.asc | File format | PerkinElmer Legacy SP |
| Sample composition | JWH-250 (1-pentyl-3-(2-methoxyphenylacetyl)indole) | CAS No. | 864445-43-2 |
| Formula | C21H23NO2 | Mol. Weight | 321.41 |
| Measurement conditions | Measured range 550.0–4000.0 cm⁻¹; Sampling interval 1.0000–1.0000 cm⁻¹; Absorbance range 0.0109–0.4168; Raw ordinate transmittance (parsed from spectrum file; instrument parameters not provided) | ||
Spectral Quality Assessment
Spectral quality assessment serves to identify sharp, broad, shoulder and other special band shapes, which are taken into account in the peak-assignment analysis below; all metrics are descriptive observations.
| Metric | Value | Verdict |
|---|---|---|
| Special band shape | broad: 1187 cm⁻¹ (FWHM 23); shoulder/overlap (half-height not independently bracketed): 1439 cm⁻¹, 1159 cm⁻¹, 1118 cm⁻¹, 738 cm⁻¹ | |
Peak Assignment Table
Evidence grades combine source tier with wavenumber window: A = direct experimental IR assignment for the same substance; B = literature assignment from a structurally analogous compound or an authoritative handbook (applicability stated per peak); C = reference substance differing substantially in structure (borrowed analogy; limitations stated per peak). Delta ≤5 cm⁻¹ gives the positive grade (A/B/C); 5–10 cm⁻¹ gives the minus grade (A-/B-/C-); delta >10 cm⁻¹ is not citable. The difference is between the literature and measured wavenumbers. Quotations are verbatim from the sources. Lowercase letters after the wavenumber denote peak intensity: s = strong (≥50% of the strongest band), m = medium (≥20%), w = weak.
| Wavenumber (cm⁻¹) | Absorbance | Evidence grade | Vibrational Assignment | Reference | Literature Excerpt (verbatim) | Note |
|---|---|---|---|---|---|---|
| 3126.0 w | 0.0410 | AΔ=1 | Indole C-H symmetric stretch | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment comes from the same-substance paper Jan E 2010: its 3125 cm-1 band is labeled indole ring C-H stretching, a difference of 1 cm-1. |
| 2947.0 m | 0.1007 | AΔ=1 | Aliphatic C-H stretch | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment is an aliphatic C-H stretch from the same-substance paper Jan E 2010: its 2946 cm-1 band is the pentyl chain CH2/CH3 asymmetric stretch, a difference of 1 cm-1. |
| 2858.0 w | 0.0757 | A-Δ=8 | N-pentyl chain CH₂/CH₃ symmetric C-H stretch | [8] Compound 2 (C₂₂H₂₅NO₂, 即 JWH-250) 表征部分，IR 数据 | “IR (KBr): 3125 νCH(indole), 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C)” | Nycz et al. fully characterised JWH-250 (compound 2, C₂₂H₂₅NO₂) by X-ray crystallography and KBr-pellet FTIR, assigning 2866 and 2837 cm⁻¹ to alkyl C-H stretching. The experimental peak at 2858 cm⁻¹ deviates by 8 cm⁻¹ from the KBr reference, within the 5–10 cm⁻¹ inter-method variation routinely observed between KBr pellet and ATR/neat-sample IR.
Limitations: Nycz et al. used KBr pellet; the present spectrum may have been recorded by ATR or neat sample. The systematic inter-method offset is typically ≤10 cm⁻¹, consistent with the observed 8 cm⁻¹ deviation. |
| 1636.0 s | 0.3380 | B-Δ=6.6 | 3-Acyl C=O stretch | [3] Section 4.4.3 (acetyl C=O stretching), p. 1040 | “The experimental ones, however, increase stepwise with the alkyl chain length from 1625.9 to 1642.6 cm−1” | This is the 3-acyl C=O stretch of JWH-250. The assignment comes from the structural-analog paper Ferenc [3] Billes 2009: the longest-chain member of its series (1-ethyl-3-acetylindole) has an experimental value of 1642.6 cm-1, a difference of 6.6 cm-1.
Applicability of the analog evidence: The 1-alkyl-3-acetylindole series is the direct model of JWH-250's carbonyl environment: a ketone C=O attached to the indole 3-position, conjuga振动分布 with the indole pi system. In JWH-250, the carbonyl carbon carries a CH2-2-methoxyphenyl group; electronically, the CH2Ar group is an alkyl substituent, the phenyl ring is not directly conjuga振动分布. Limitations: The quo振动分布 experimental wavenumber is the series maximum (1-ethyl-3-acetylindole), a difference of 6.6 cm-1 from the sample. Since N-pentyl is longer than N-ethyl, the N-alkyl shift direction supports 1636-1640 cm-1. The analog data are from a series that does not include a methoxyphenylacetyl substituent. |
| 1609.0 m | 0.1455 | B-Δ=7 | Indole ring C=C stretch | [1] Table 2, row v10, p. 41 | “v10 A' 1616 1610 1654 1625 νCC(59)ring” | The assignment is based on the structural analog 1-methylindole from Çağlar [1] Karaca 2025, whose 1616 cm-1 band differs by 7 cm-1.
Applicability of the analog evidence: N-alkylindole ring C=C stretching is shared with 1-methylindole. Ring-skeleton motions are robust to substitution. Limitations: 1-Methylindole lacks the 3-acyl and methoxyphenyl substituents. The analog data are ATR while sample conditions are unknown. |
| 1575.0 w | 0.0755 | AΔ=0 | Indole ring C=C stretch | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment comes from the same-substance paper Jan E 2010, whose 1575 cm-1 band differs by 0 cm-1.
Applicability of the analog evidence: Indole ring C=C stretching is shared with the N-alkylindole skeleton. |
| 1524.0 s | 0.2216 | B-Δ=8 | Indole C=C stretch, N-CH3 bend | [1] Table 2, row v12, p. 41 | “v12 A' 1516 1513 1552 1526 νC=C(48), δNCH (11)” | The assignment is based on the structural analog 1-methylindole from Çağlar [1] Karaca 2025, whose 1516 cm-1 band differs by 8 cm-1.
Applicability of the analog evidence: Indole ring C=C stretching is shared between the compounds. [7] Kanaoka 1960's aromatic band group at 1520-1470 cm-1 (the indole C=C region) supports this region. Limitations: The small in-plane bending component refers to the N-CH3 group of 1-methylindole. JWH-250 has N-pentyl instead, so that small component does not transfer. 1-Methylindole also lacks the 3-acyl and methoxyphenyl substituents. The analog data are ATR while sample conditions are unknown. |
| 1486.0 m | 0.1675 | BΔ=3 | Methoxyphenyl ring C-C stretch | [4] Section 3.5 (C=C and C-C vibrations), p. 655; Table 4 row 1483/νCC, p. 659 | “The C-C single bond is observed at 1483 cm-1 in FT-IR” | The assignment is based on the structural analog 4-methoxyacetophenone from [4] Srinivasan 2019, whose 1483 cm-1 band differs by 3 cm-1.
Applicability of the analog evidence: 4-Methoxyacetophenone shares the methoxy-substitu振动分布 benzene ring (the Ar-OCH3 fragment). Its ring C-C stretch at 1483 cm-1 transfers to JWH-250's 2-methoxyphenyl ring. [6] Bartyzel 2018 compound 2 at 1481 cm-1 (difference of 5 cm-1) and [1] Karaca 2025 at 1488 cm-1 (difference of 2 cm-1, an N-CH3-rela振动分布 component) support it. Limitations: The analog has para-methoxy substitution while JWH-250 is ortho. The side chain differs (Ar-CO-CH3 vs indolyl-CO-CH2Ar). The analog data are KBr pellets while sample conditions are unknown. The source is a single-author journal. |
| 1454.0 s | 0.2467 | BΔ=2 | Methoxy methyl in-plane bend | [5] Table 2, row 1452, p. 9 | “1452 m 1435 δ(Me)” | The assignment comes from the structural-analog paper Julia [5] Polak 2024: its 1452 cm-1 band differs from the sample by 2 cm-1.
Applicability of the analog evidence: The OCH3 methyl deformation of the analog's 5-methoxy group is shared with JWH-250's 2-methoxyphenyl OCH3: both are aryl methyl ether CH3 deformations. Limitations: The measured 1454 cm-1 band is composite. It also carries pentyl-chain CH2 scissoring (about 1465 cm-1), pentyl CH3 asymmetric deformation, and indole ring contributions not covered by this assignment. The analog also has COOH and N-H, which perturb ring modes. KBr data vs unknown sample conditions. |
| 1439.0 m | 0.2040 | BΔ=5 | Indole five/six ring stretch | [5] Table 2, row 1434, p. 9 | “1434 s 1431 ν(R5/R6)” | The assignment comes from the structural-analog paper Julia [5] Polak 2024: its 1434 cm-1 band differs from the sample by 5 cm-1.
Applicability of the analog evidence: Indole ring stretching is shared: both are indole derivatives. The five/six-membered ring stretch at 1434-1439 cm-1 is robust to substitution. Limitations: The analog's ring substitution (5-OCH3, 2-COOH) differs from JWH-250 (3-acyl, N-pentyl). The analog has N-H rather than N-alkyl. KBr data vs unknown sample conditions. |
| 1389.0 s | 0.2175 | AΔ=0 | Indole ring stretch + C-H bend | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment comes from the same-substance paper Jan E 2010: its 1389 cm-1 band differs from the sample by 0 cm-1. The vibration is a mixed mode, composed of ring C-C 39%, C-N 15%, and C-H bending 16%.
Applicability of the analog evidence: Indole ring-skeleton stretching is shared with 1-methylindole: the same five-membered-ring C-C/C-N mix. Limitations: 1-Methylindole lacks the 3-acyl and methoxyphenyl substituents. [6] Bartyzel 2018 compound 2 at 1386 cm-1 (difference of 3 cm-1) supports the assignment. ATR data vs unknown sample conditions. |
| 1352.0 m | 0.1153 | BΔ=1 | Methyl C-H and C-N-C ring bend | [6] Table 3 (compound 2), p. 940 | “1351 (m) 1400 1347 δHCH (15), CHCNC (30)” | The assignment comes from the structural-analog paper Agata [6] Bartyzel 2018: its 1351 cm-1 band differs from the sample by 1 cm-1, which is close to the analog. The vibration is a mixed mode, composed of C-H bending 15% and ring C-N-C deformation 30%.
Applicability of the analog evidence: JWH-250 carries methyl groups (OCH3 and the pentyl terminal CH3) whose C-H deformation is the shared coordinate. The indole ring C-N-C deformation is shared with the indole skeleton. Limitations: The band is a mixed mode; only 45% of the potential-energy distribution is lis振动分布. The analog is 1,2,3,5-tetrasubstitu振动分布 (no C2-H/C3-H), so its ring deformation pattern differs from JWH-250's 1,3-disubstitu振动分布 indole. ATR data vs unknown sample conditions. |
| 1331.0 m | 0.1131 | BΔ=0 | Indole ring C-C/C-N stretch | [1] Table 2, row v20, p. 41 | “v20 A' 1331 1331 1357 1334 νCC(53)ring1, νCN(19)” | The literature value of 1331 cm-1 is assigned to the indole ring C-C and C-N skeleton stretching vibration. The measured peak is at 1331 cm-1, a difference of 0 cm-1.
Applicability of the analog evidence: This vibration is shared with 1-methylindole, as both contain the same indole ring. Limitations: The analog lacks the 3-acyl and methoxyphenyl substituents. Data were collec振动分布 in ATR mode; sample conditions are unknown. |
| 1300.0 m | 0.1687 | BΔ=0 | Indole ring in-plane bend | [5] Table 2, row 1300, p. 9 | “1300 w 1282 δ(R5/R6)” | No qualifying literature assignment was found. This peak is most likely the indole ring in-plane bending vibration.
Applicability of the analog evidence: The reference compound shares the indole ring skeleton. Its band at 1300/1282 cm⁻¹ is assigned to in-plane ring deformation, which is transferable to the indole moiety in the target compound. Limitations: The reference compound carries different alkyl/methoxy substitution patterns; conjugation and substituent effects may shift peak positions by a few cm⁻¹. |
| 1245.0 s | 0.2821 | BΔ=2 | Indole C-H bend, C-C stretch | [1] Table 2, row v22, p. 41 | “v22 A' 1243 1239 1268 1247 νCC(18), δCCH(41), δNCH(10)” | The literature value of 1243 cm-1 is assigned to indole ring C-H bending, mixed with C-C stretching and a minor N-CH3 component. The measured peak is at 1245 cm-1, a difference of 2 cm-1. This band may also contain contribution from the 2-methoxyphenyl C-O-C stretch.
Applicability of the analog evidence: This vibration is shared with 1-methylindole, as both compounds contain the same indole ring structure. Limitations: The N-CH3 group of 1-methylindole differs from the N-pentyl chain of JWH-250, so that component is not transferable. The measured peak may also have a strong methoxyphenyl C-O-C contribution not covered by this assignment. Data were collec振动分布 in ATR mode; sample conditions are unknown. |
| 1216.0 s | 0.3092 | BΔ=4 | Aryl methyl ether C-O stretch | [5] Table 2, row 1220, p. 9 | “1220 vs 1205 ν(C5O3), δ(O3C5), δ(R5/R6)” | The literature value of 1220 cm-1 is assigned to the aryl methyl ether C-O stretch, mixed with O-C in-plane bending and ring bending. The measured peak is at 1216 cm-1, a difference of 4 cm-1.
Applicability of the analog evidence: This vibration arises from the methoxy group attached to an aromatic ring. JWH-250 contains the same methoxy group on its 2-methoxyphenyl moiety. Limitations: The methoxy group of the analog is attached to the indole ring, while in JWH-250 it is on a separate phenyl ring, representing a positional difference. The analog also contains a carboxylic acid and N-H group. The measured peak may also contain indole C-H bending character, not covered by this assignment. Data were collec振动分布 in KBr; sample conditions are unknown. |
| 1187.0 m | 0.1499 | BΔ=5 | Methoxy C-O stretch | [6] Table 3 (compound 2), p. 940 | “1182 (m) 1213 1167 νOC (26)” | This peak is assigned to the methoxy C-O stretch. A structural analog in the literature shows this vibration at 1182 cm-1, a wavenumber difference of 5 cm-1.
Applicability of the analog evidence: The analog carries two aryl OCH3 groups. Its methoxy C-O stretch at 1182 cm-1 transfers to JWH-250's 2-methoxyphenyl OCH3. Limitations: The potential-energy distribution is partial: 26% is C-O stretch, the rest is unlis振动分布, and the band is mixed. The analog is tetrasubstitu振动分布 while JWH-250 is 1,3-disubstitu振动分布. The sample band at 1187 cm-1 may also carry indole ring C-H in-plane bending. ATR data vs unknown sample conditions. |
| 1159.0 m | 0.1302 | BΔ=5 | Indole ring C-H in-plane bend | [1] Table 2, row v24, p. 41 | “v24 A' 1154 1177 1157 νCC(18)ring1, δCCH(69)ring1” | This peak is assigned to the indole six-membered-ring C-H in-plane bend. A structural analog in the literature shows this vibration at 1154 cm-1, a wavenumber difference of 5 cm-1.
Applicability of the analog evidence: Indole six-membered-ring C-H in-plane bending is the shared motion: the same ring of the N-alkylindole core. Limitations: 1-Methylindole lacks the 3-acyl and methoxyphenyl substituents. The sample band may carry OCH3 C-O-C character not in this assignment. ATR data vs unknown sample conditions. |
| 1140.0 s | 0.2293 | B-Δ=6 | Indole ring C-H in-plane bend | [1] Table 2, row v25, p. 41 | “v25 A' 1134 1135 1157 1137 νCC(23)ring1, δCCH(42)ring1” | This peak is assigned to the indole six-membered-ring C-H in-plane bend. A structural analog in the literature shows this vibration at 1134 cm-1, a wavenumber difference of 6 cm-1.
Applicability of the analog evidence: Indole six-membered-ring C-H in-plane bending with ring C-C stretch is shared with the N-alkylindole core. Limitations: 1-Methylindole has different substitution. The strong sample band at 1140 cm-1 may include methoxyphenyl-ring C-H in-plane character not covered by this assignment. ATR data vs unknown sample conditions. |
| 1118.0 m | 0.1053 | B-Δ=10 | Aromatic C-H in-plane bend | [6] Table 3 (compound 2), p. 940 | “1108 (m) 1166 1122 δHCC (26)” | This peak is assigned to the aromatic C-H in-plane bend. A structural analog in the literature shows this vibration at 1108 cm-1, a wavenumber difference of 10 cm-1, which is relatively close for this type of analog.
Applicability of the analog evidence: Aromatic C-H in-plane bending is the plausible motion for the 1118 cm-1 band: C-H in-plane bending of the indole ring and/or the methoxyphenyl ring. The analog band is the same C-H bending motion. Limitations: The wavenumber difference is 10.0 cm-1. The potential-energy distribution is partial: 26% C-H bending, the rest unlis振动分布. The analog is tetrasubstitu振动分布, so its C-H pattern differs from JWH-250's 1,3-disubstitu振动分布 indole. ATR data vs unknown sample conditions. |
| 1101.0 m | 0.1541 | BΔ=0 | Indole benzene-ring C-H bend | [5] Table 2, row 1101, p. 9 | “1101 w 1102 δ(C6H), δ(C7H)” | This peak is assigned to indole benzene-ring C-H in-plane bending, based on [5] Polak 2024 at 1101 cm-1 (difference of 0 cm-1).
Applicability of the analog evidence: Indole benzene-ring C-H in-plane bending is present in the analog, and this vibration is relatively insensitive to ring substitution. Limitations: The analog has different ring substituents (2-COOH, 5-OCH3) compared to JWH-250 (3-acyl, N-pentyl). The analog was measured in KBr, while sample conditions are unknown. |
| 1069.0 m | 0.1268 | BΔ=5 | Methoxyphenyl C-H in-plane bend | [4] Section 3.5 (C-H vibrations), p. 655; Table 4 row 1064/βCH, p. 659 | “The FT-IR values are found at 1315, 1278, 1278, 1197 and 1064 cm-1” | This peak is most likely the methoxyphenyl ring C-H in-plane bending. No direct assignment at 1069 cm-1 was found in same-substance literature.
Applicability of the analog evidence: This vibrational mode is applicable to JWH-250's 2-methoxyphenyl ring, as both share the same Ar-OCH3 fragment. Limitations: The analog has para-methoxy substitution, while JWH-250 has ortho-methoxy; this changes the ring C-H in-plane pattern. The band may also include indole ring C-H character. The analog was measured in KBr; sample conditions are unknown. |
| 1052.0 m | 0.1336 | BΔ=1 | Aryl methoxy (Ar-OCH₃) C-O-C stretch; possible indole ring C-O contribution | [9] Table 2 (solid-state column, C-O-C row), p. 182 | “C-O-C 1280 cm–1 strong asym- metric. and 1053 cm–1 very weak asymmetric.” | No direct assignment for 1052 cm−1 was found in same-substance literature. This assignment follows from Thaçi et al. 2023: B2MBCP (bis(2-methoxybenzylidene)cyclopentanone) contains the same ortho-methoxy-phenyl (Ar-OCH₃) fragment as JWH-250; the C-O-C asymmetric stretch appears at 1053 cm−1 (weak band) in solid-state KBr FTIR, delta 1 cm−1.
Applicability of the analog evidence: The two 2-methoxybenzylidene units of B2MBCP provide the same Ar-OCH₃ fragment as the 2-methoxyphenyl group of JWH-250 (both ortho-methoxy); the local bonding environment of the methoxy C-O-C stretch (Ar-O-CH₃) matches one-to-one, so the vibrational coordinate transfers directly. Limitations: The 1053 cm−1 band is labelled very weak in the source table; the carbonyl of B2MBCP is a cyclopentanone (not an indole 3-acyl), but the C-O-C vibration involves only the methoxy–phenyl local environment; the source solid-state spectrum is KBr pellet and the sample measurement conditions are unknown. |
| 1032.0 m | 0.1750 | AΔ=3 | Aryl methyl ether C-O stretch mixed with ring stretch | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | This peak is assigned to aryl methyl ether C-O stretch mixed with ring stretch, based on the same-substance paper Jan E 2010, whose 1029 cm-1 band differs by 3 cm-1.
Applicability of the analog evidence: The aryl OCH3 C-O stretch (symmetric C-O-C of an aryl methyl ether) is shared between the analog and JWH-250's 2-methoxyphenyl group. Limitations: The analog's methoxy group is on the indole 5-position, while JWH-250's methoxy is on a separate phenyl ring. The analog also contains COOH and N-H groups. The analog was measured in KBr; sample conditions are unknown. |
| 1011.0 m | 0.1222 | BΔ=3 | Indole C-C stretch, C-H bend | [1] Table 2, row v29, p. 41 | “v29 A' 1014 1010 1036 1018 νCC(61)ring1, δCCH(17)” | The assignment comes from the structural analog Çağlar [1] Karaca 2025. Its 1-methylindole 1014 cm⁻¹ band differs from the sample by 3 cm⁻¹.
Applicability of the analog evidence: Indole six-membered-ring C-C stretching is shared with 1-methylindole (the same ring of the N-alkylindole core). Limitations: 1-Methylindole lacks the 3-acyl and methoxyphenyl substituents. ATR data vs unknown sample conditions. |
| 964.0 w | 0.0830 | BΔ=5 | Aromatic C-H out-of-plane bend | [1] Table 2, row v31, p. 41 | “v31 A" 959 973 957 γCH(88)” | The assignment comes from the structural analog Çağlar [1] Karaca 2025. Its 1-methylindole 959 cm⁻¹ band differs from the sample by 5 cm⁻¹.
Applicability of the analog evidence: Aromatic ring C-H out-of-plane bending is shared with the N-alkylindole core. [6] Bartyzel 2018 compound 2 at 963 cm⁻¹ (difference of 1 cm⁻¹) supports it. Limitations: 1-Methylindole has different substitution. The sample band may include methoxyphenyl-ring C-H out-of-plane character. ATR data vs unknown sample conditions. |
| 923.0 m | 0.1245 | AΔ=1 | Aromatic C-H out-of-plane bend | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment comes from the same-substance paper Jan E 2010. Its 922 cm⁻¹ band differs from the sample by 1 cm⁻¹. |
| 872.0 m | 0.0911 | B-Δ=9 | Indole in-plane deformation | [1] Table 2, row v33, p. 41 | “v33 A' 881 881 896 881 νCC(13), δCCC(40), δCCH(16)” | The assignment comes from the structural analog Çağlar [1] Karaca 2025. Its 1-methylindole 881 cm⁻¹ band differs from the sample by 9 cm⁻¹, which is relatively close for an analog.
Applicability of the analog evidence: Indole ring in-plane deformation (domina振动分布 by ring-angle bending) is shared with the N-alkylindole skeleton. Limitations: The difference of 9 cm⁻¹ is near the limit. 1-Methylindole has different substitution. ATR data vs unknown sample conditions. |
| 858.0 m | 0.1029 | B-Δ=10 | Aromatic C-H out-of-plane bend | [6] Table 3 (compound 2), p. 941 | “848 (m) 887 853 CHCCC (71)” | The assignment comes from [6] Bartyzel 2018. Its experimental band at 848 cm⁻¹ differs by 10 cm⁻¹.
Applicability of the analog evidence: Aromatic C-H out-of-plane bending is the plausible motion for the 858 cm⁻¹ band: C-H out-of-plane bending of the indole ring and/or the methoxyphenyl ring. The analog band is the same motion. Limitations: The analog is tetrasubstitu振动分布, so its out-of-plane C-H pattern differs from JWH-250's 1,3-disubstitu振动分布 indole plus 1,2-disubstitu振动分布 benzene. ATR data vs unknown sample conditions. |
| 792.0 m | 0.1875 | AΔ=0 | Indole C3-H out-of-plane bend | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment comes from the same-substance paper Jan E 2010, whose experimental band at 792 cm⁻¹ differs by 0 cm⁻¹. The C3-H out-of-plane detail comes from [7] Kanaoka 1960's characteristic 785-770 cm⁻¹ region for 3-substitu振动分布 indoles; measured to the upper bound, the difference is 7 cm⁻¹.
Applicability of the analog evidence: JWH-250 is a 3-substitu振动分布 indole; the C3-H out-of-plane bending region 785-770 cm⁻¹ for 3-substitu振动分布 indoles matches the substitution pattern directly (Kanaoka compares indoles with and without C3-H). Limitations: This is a 1960 region-type tentative assignment, not a normal-mode analysis. The difference of 7 cm⁻¹ is measured to the upper bound of 785 cm⁻¹. The scan is OCR-transcribed, so individual characters may be imperfect. KBr data vs unknown sample conditions. |
| 756.0 s | 0.4167 | AΔ=2 | Indole ring deformation | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment comes from the same-substance paper Jan E 2010, whose experimental band at 758 cm⁻¹ differs by 2 cm⁻¹. The vibration composition comes from a normal-mode analysis: ring C-C 47%, C-N 10%, ring-angle bending 13%.
Limitations: 1-Methylindole lacks the 3-acyl and methoxyphenyl substituents. The sample's strongest band likely also carries methoxyphenyl-ring C-H out-of-plane character not covered by this assignment. ATR data vs unknown sample conditions. |
| 738.0 s | 0.2959 | AΔ=1 | Aromatic C-H out-of-plane bend | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | The assignment comes from the same-substance paper Jan E 2010, whose experimental band at 737 cm⁻¹ differs by 1 cm⁻¹.
Applicability of the analog evidence: Aromatic ring C-H out-of-plane bending is shared with the N-alkylindole core, consistent with the ortho-disubstitu振动分布 benzene pattern. Limitations: 1-Methylindole has different substitution. [6] Bartyzel 2018 compound 2 at 738 cm⁻¹ shows a ring-deformation motion at the same position, so the coordinate assignment at this position is ambiguous. ATR data vs unknown sample conditions. |
| 705.0 m | 0.1820 | B-Δ=6 | N-C(pentyl) stretch, ring bend | [1] Table 2, row v39, p. 41 | “v39 A' 711 711 723 711 νC16-N(25), δCCC(23), δCCH(14)” | This peak is assigned to N-C(pentyl) stretching mixed with indole ring deformation, based on [1] Karaca 2025. Their experimental wavenumber is 711 cm-1, a difference of 6 cm-1 from the sample. The vibration is composed of 25% N-C, 23% ring angle bending, and 14% C-H bending.
Applicability of the analog evidence: N-C(pentyl) stretching and indole ring deformation are shared with the N-alkylindole skeleton. 1-Methylindole has N-CH3 while JWH-250 has N-pentyl, but the N-C stretching motion persists. Limitations: The N-C component refers to the N-CH3 carbon of 1-methylindole; the chain length differs. 1-Methylindole lacks the 3-acyl and methoxyphenyl substituents. ATR data vs unknown sample conditions. |
| 646.0 s | 0.2472 | AΔ=1 | C-C out-of-plane deformation | [8] Experimental section, compound 2, p. 126 | “IR (KBr) 3125 νCH(indole); 2946, 2924 νPhH, 2866, 2837 νCH(alkyl), 1707 νC=O, 1638, 1608 νC=N, 1575 νC=C, 1389 νC–O–C, 1029 δ(C–O–C), 922, 758, 737 δ(C–H out of the plane), 792, 647 δ(C–C out of the plane)” | This peak is assigned to C-C out-of-plane deformation, based on the same-substance paper Jan E 2010. Their experimental wavenumber is 647 cm-1, a difference of 1 cm-1 from the sample. |
| 600.0 m | 0.1528 | B-Δ=6 | Ring out-of-plane deformation | [6] Table 3 (compound 2), p. 941 | “606 (m) 632 608 CHCCC (14), CCCCC (34), COCCC (20)” | This peak is assigned to aromatic ring out-of-plane deformation, based on [6] Bartyzel 2018. Their experimental wavenumber is 606 cm-1, a difference of 6 cm-1 from the sample.
Applicability of the analog evidence: Indole ring out-of-plane deformation (ring-puckering type, 34% ring out-of-plane) is the shared motion. The C-O-C out-of-plane component relates to the aryl OCH3, a shared fragment. Limitations: The mode is mixed: 34% ring out-of-plane plus C-H out-of-plane and C-O-C out-of-plane. The analog is tetrasubstitu振动分布 vs JWH-250's 1,3-disubstitu振动分布 indole. ATR data vs unknown sample conditions. |
| 574.0 m | 0.1612 | BΔ=1 | Indole out-of-plane deformation | [1] Table 2, row v42, p. 41 | “v42 A" 573 573 583 573 φPhenyl(44), τCCCN(25)” | This peak is assigned to indole ring out-of-plane deformation/torsion, based on [1] Karaca 2025. Their experimental wavenumber is 573 cm-1, a difference of 1 cm-1 from the sample. The vibration is composed of 44% phenyl torsion and 25% ring torsion.
Applicability of the analog evidence: Indole ring out-of-plane deformation/torsion is shared with the N-alkylindole skeleton. Limitations: 1-Methylindole lacks the 3-acyl and methoxyphenyl substituents. The sample band may also carry C=O in-plane bending, so the coordinate at 574-578 cm-1 is ambiguous. ATR data vs unknown sample conditions. |
| 555.0 m | 0.1537 | B-Δ=9 | OCH3 C-O-C out-of-plane bend | [6] Table 3 (compound 2), p. 941 | “564 (w) 575 553 COCCC (10)” | This peak is assigned based on the work of Agata [6] Bartyzel 2018. In the structural analog, the methoxy C-O-C out-of-plane deformation appears at 564 cm⁻¹, which is a difference of 9 cm⁻¹ from the JWH-250 peak.
Applicability of the analog evidence: The aryl methyl ether C-O-C out-of-plane deformation exists in both the analog's OCH3 groups and JWH-250's 2-methoxyphenyl OCH3. Limitations: The assignment is weak: only 10% of the potential-energy distribution (C-O-C out-of-plane) is lis振动分布. The band is weak in the source. The analog is tetrasubstitu振动分布 vs JWH-250's 1,3-disubstitu振动分布 indole. The difference of 9 cm-1 is near the limit. ATR data vs unknown sample conditions. |
References
- Çağlar Karaca. Spectroscopic (FT-Raman, FT-IR, UV-Vis, and NMR) and Theoretical Analysis of 1-Methylindole: Structural Characterization, Non-Covalent Interactions, and Electronic Properties. Celal Bayar Üniversitesi Fen Bilimleri Dergisi, 2025 10.18466/cbayarfbe.1554031
- Tania M. G. Salerno, Paola Donato, Giampietro Frison, Luca Zamengo, Luigi Mondello. Gas Chromatography—Fourier Transform Infrared Spectroscopy for Unambiguous Determination of Illicit Drugs: A Proof of Concept. Frontiers in Chemistry, 2020 10.3389/fchem.2020.00624
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- Julia Polak, Julia Bąkowicz, Barbara Morzyk-Ociepa. Discovery of a New Polymorph of 5-Methoxy-1H-Indole-2-Carboxylic Acid: Characterization by X-ray Diffraction, Infrared Spectroscopy, and DFT Calculations. Molecules, 2024 10.3390/molecules29102201
- Agata Bartyzel, Agnieszka A. Kaczor, Halina Głuchowska, Monika Pitucha, Tomasz M. Wróbel, Dariusz Matosiuk. Thermal and spectroscopic studies of 2,3,5-trisubstituted and 1,2,3,5-tetrasubstituted indoles as non-competitive antagonists of GluK1/GluK2 receptors. Journal of Thermal Analysis and Calorimetry, 2018 10.1007/s10973-018-7146-6
- Yuichi Kanaoka, Yoshio Ban, Takeshi Oishi, Osamu Yonemitsu, Masanao Terashima, Tetsuo Kimura, Masako Nakagawa. Infrared Spectra of Some Indole and Pyrrole Compounds. Chemical and Pharmaceutical Bulletin, 1960 10.1016/0584-8539(79)80064-5
- Jan E. Nycz, Grzegorz Małecki, Michał Zawiazalec, Tomasz Paździorek. X-ray structures and computational studies of 1-pentyl-3-(4-methoxy-1-naphthoyl)indole and 2-(2-methoxy-phenyl)-1-(1-pentyl-1H-indol-3-yl)-ethanone. Journal of Molecular Structure, 2010, 984: 125-130 10.1016/j.molstruc.2010.09.016
- Veprim Thaçi, Arianit A. Reka, Nataša Ristovska, Ramiz Hoti, Avni Berisha, Jane Bogdanov. Experimental and theoretical studies of (2E,5E)-2,5-bis(2-methoxybenzylidene)cyclopentanone: Structural, electrochemical, and spectroscopic features, solid-state interactions, molecular docking, and adsorption studies onto 2D carbon nanomaterials. Macedonian Journal of Chemistry and Chemical Engineering, 2023, 42(2): 175-194 10.20450/mjcce.2023.2727
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