• Top library match: ethyl 2-diethoxyphosphorylacetate #24276

• The 1102 cm⁻¹ band has an alternative literature assignment to C–S bonding [13], which is absent in the proposed phosphonate ester; the stronger C–O ether/ester assignment is preferred.
• A few weaker features (725 cm⁻¹ cis‑double bonds, 1407 cm⁻¹ carbonate) are not intrinsic to a pure phosphonate ester and may arise from trace unsaturation or absorbed CO₂.
• The presence of minor carboxyl and carbonate signals raises the possibility of a mixture or partial hydrolysis/degradation.
• Phosphonate‑specific P=O stretching is not fully resolved; deconvolution of the broad 1266 cm⁻¹ region would improve confidence.
• The library match, although strong, does not guarantee the exact isomer distribution or purity of the sample.

Recommended next steps: Compare the sample spectrum with an authentic ethyl 2‑diethoxyphosphorylacetate standard to confirm the full band profile. Acquire ³¹P NMR or Raman data to unambiguously identify the phosphonate environment and rule out overlapping ester mixtures. Perform thermal analysis (TGA/DSC) to assess sample purity and detect any inorganic contaminants that could account for the 668 and 1407 cm⁻¹ peaks.