What absorbs at 850 cm⁻¹ in an FTIR spectrum?

Quick answer

A band near 850 cm⁻¹ is usually interpreted by checking which functional groups repeatedly co-occur there in the literature, then confirming at least one or two additional peaks in the same sample. This page ranks those assignments by accumulated evidence rather than by a single fixed textbook rule.

Possible functional-group assignments

Ranking reflects accumulated literature evidence, not a single fixed rule. Always confirm against your sample context.

Spectrum logic

This band becomes meaningful only when read with its neighboring peaks. In practice, analysts first look at the assignments above, then check whether the same sample also shows other peaks expected for the same structural motif. A lone band near 850 cm⁻¹ is usually not enough for material identification by itself.

Real-world usage

This type of query is common in polymer identification, unknown plastic screening, QC troubleshooting, recycled-material verification, and literature-backed peak assignment review.

Common mistakes

• Treating one isolated band as proof of a material without checking at least one or two supporting peaks.
• Ignoring overlap: multiple functional groups can contribute near the same wavenumber.
• Skipping validation when additives, blends, oxidation, or contamination may distort the spectrum.

Verification advice

When ambiguity remains, validate the hypothesis with DSC, GC-MS, or TGA, especially for blends, degraded samples, and filled polymers.

Literature behind these assignments

• Borate confidence 1.0

  “LLM confirmed rule peak-group candidate”

  Dalui 等 - 2008 - Boron phosphide films prepared by co-evaporation t DOI: 10.1016/j.tsf.2007.09.047
• Silicon nitrogen confidence 1.0

  “2(cid:3)1019 [15] Si-N Si-N local distorted 790 stretching 2(cid:3)1019 Si-N N-Si3 asymmetric stretching 850 [15] 2(cid:3)1019 950 [15] Si-N Si-N stretching of H-SiN3 Si-O Si-O symmetric stretching 1040 - [2,16]”

  Effect of PECVD silicon oxynitride film composition on the surface passivation of silicon wafers DOI: 10.1016/j.solmat.2011.09.052
• Aromatic ring confidence 1.0

  “Jardine et al., 2015), and are reduced in height andEandFthearomatic/hydroxylratiofromtheunstandardisedspectra.Barcolours whenthesporopolleninisisolated.Inthecurrentstudythisisobserved relatetothelevelofshading:white=open(unshaded)sample,li”

  Shedding light on sporopollenin chemistry, with reference to UV reconstructions DOI: 10.1016/j.revpalbo.2016.11.014
• Phosphate (PO4) confidence 1.0

  “The phosphate peaks above 850 °C.”

  Lebon 等 - 2008 - Characterization of archaeological burnt bones co DOI: 10.1007/s00216-008-2469-y
• Acetate confidence 1.0

  “In the pure rutin spectrum, the transmission peaks observed at 1690, 1235 and and 850 cm-1 were assigned to the C=O stretching vibration of aryl ketones, C-O phenol cm-1 850 were assigned to the C=O stretching vibration of aryl ketones, C-O”

  Synthesis of Zinc Oxide Nanoparticles with Bioflavonoid Rutin: Characterisation, Antioxidant and Antimicrobial Activities and In Vivo Cytotoxic Effects on Artemia Nauplii DOI: 10.3390/antiox11101853
• Alkyl C-H confidence 1.0

  “For the degradation of reactive violet (RV) 1 by the ligninolytic enzymes of the strain Ganoderma cupreum AG-1, the peaks at 1,602 and 1,434 cm-1 may be characteristics of C=C aromatic skeletal vibration and azo linkages (-N=N-) on aromatic”

  Trichoderma asperellum laccase mediated crystal violet degradation–Optimization of experimental conditions and characterization DOI: 10.1016/j.jece.2016.11.044
• Metal oxygen confidence 1.0

  “The peak visible at 850 is likely appears at 750 Ti-O-Ti to be derived from stretching.”

  Sunarso 等 - 2008 - Characterization of hybrid organic and inorganic f DOI: 10.1016/j.ssi.2008.02.066
• Alkyl C-H confidence 1.0

  “In addition, the functionalcm-1, group profile also shows bending vibrations at 850 and 1420 also representing C-H stretching.”

  The effect of Ag nanoparticles in Ag/polyvinyl alcohol nanofiber composites DOI: 10.1007/s00289-020-03528-2