High Pressure Structural Investigation of Benzoic Acid: Raman Spectroscopy and X-ray Diffraction

Abstract

The structural stability of benzoic acid (C 6 H 5 COOH, BA), a hydrogen-bonded molecular crystal, has been investigated by Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) up to ~ 18 GPa at room temperature. Under ambient conditions, benzoic acid molecules are arranged in two set of parallel planes and held together by hydrogen bonding and van der Waals interactions. Small changes (e.g., emergence of new peaks, splitting of original peaks) can be observed in the Raman spectra at high pressures. However, no obvious changes can be observed in the X-ray diffraction measurements, which rules out any symmetry/structure changes within this pressure range. The pressure dependence of lattice parameters are presented, which show monotonously decrease without any anomalies. The experimental isothermal pressure-volume data are well fitted by the third-order Birch-Murnaghan equation of state, yielding bulk modulus 0 B = 41.7(6) GPa and a first pressure derivative ' 0 B = 4.5(4). Axial compressibility shows obvious anisotropy, the a-axis is more compressible than b-axis and c-axis. Moreover, the near symmetrization limit of hydrogen bonds at high pressures is proposed from the first-principles calculations.Based on the Raman, XRD, and the first-principles calculations analysis, we propose that the high pressure structural stability of benzoic acid is associated with the special hydrogen-bonded dimer structure.

Non-Invasive Characterization of Single-, Double- and Triple-Viral Diseases of Wheat With a Hand-Held Raman Spectrometer

“…1630 cm -1 can be assigned to the aromatic ring and C=C-C of ring vibrations in phenylpropanoids (Agarwal, 2006;Kang et al, 2016;Pompeu et al, 2017). The band at 1326 cm -1 , associated with CH 2 vibrations, could potentially be assigned to carbohydrates or phenylpropanoids.…”

“…BYDV (shortened to B) alone, like W, could not be uniquely identified using ANOVA. However, at 1051 cm -1 , B, WB and Band (cm -1 ) Vibrational mode Assignment 522 (vw) n(C-O-C) glycosidic cellulose (Edwards et al, 1997) 747 (w) g(C-O-H) of COOH pectin (Synytsya et al, 2003) 915 (w) n(C-O-C) in plane, symmetric cellulose, lignin (Edwards et al, 1997(Edwards et al, ) 1000 in-plane CH 3 rocking of polyene carotenoids (Adar, 2017;Devitt et al, 2018Devitt et al, ) 1051 n(C-O)+n(C-C)+d(C-O-H) cellulose, phenylpropanoids (Edwards et al, 1997(Edwards et al, ) 1070 n(CO) of secondary alcohol cellulose (Edwards et al, 1997(Edwards et al, ) 1115 sym n(C-O-C), C-O-H bending cellulose (Edwards et al, 1997(Edwards et al, ) 1156 asym n(C-C) ring breathing carotenoids (Jehlicǩa et al, 2014), cellulose (Edwards et al, 1997(Edwards et al, ) 1186 n(C-O-H) next to aromatic ring+s (CH) xylan (Mary et al, 2012;Agarwal, 2014Agarwal, ) 1218 d(C-C-H) aliphatics (Yu et al, 2007), xylan (Agarwal, 2014(Agarwal, ) 1288 d(C-C-H) aliphatics (Yu et al, 2007(Yu et al, ) 1326 dCH 2 bending vibration cellulose, phenylpropanoids (Edwards et al, 1997(Edwards et al, ) 1382 dCH 2 bending vibration aliphatics (Yu et al, 2007(Yu et al, ) 1440 d(CH 2 )+d(CH 3 ) aliphatics (Yu et al, 2007(Yu et al, ) 1455 dCH 2 bending vibration aliphatics (Yu et al, 2007(Yu et al, ) 1525 -C=C-(in plane) carotenoids (Adar, 2017;Devitt et al, 2018Devitt et al, ) 1601 n(C-C) aromatic ring+s(CH) phenylpropanoids (Agarwal, 2006;Kang et al, 2016…”

Raman Spectroscopy Enables Non-invasive and Confirmatory Diagnostics of Salinity Stresses, Nitrogen, Phosphorus, and Potassium Deficiencies in Rice

“…Aliphatic (Yu et al, 2007) 1488 δ(CH 2 ) + δ(CH 3 ) Aliphatic (Yu et al, 2007) 1527-1545 -C = C-(in plane) Carotenoids (Adar, 2017;Devitt et al, 2018) 1601-1604 ν(C-C) aromatic ring + σ(CH) Phenylpropanoids (Stewart et al, 2001;Agarwal, 2006;Jurasekova et al, 2006;Kang et al, 2016) 1674 C = O stretching, amide I Proteins (Devitt et al, 2018) Raman Spectroscopy…”

Detection and identification of canker and blight on orange trees using a hand‐held Raman spectrometer

“…Vibrational mode Assignment 747 γ(C─O─H) of COOH Pectin [25] 915 ν(C─O─C) in plane, symmetric Cellulose and lignin [26] 1,000 ν 3 (C─CH 3 stretching) and phenylalanine Carotenoids and protein [27,28] 1,155 asym ν(C─C) ring breathing Carbohydrates and cellulose [26] 1,184 ν(C─O─H) next to aromatic ring+σ (CH) Xylan [29,30] 1,218-1,226 δ(C─C─H) Aliphatic [31] and xylan [29] 1,247 C─O stretching (aromatic) Lignin [32] 1,288 δ(C─C─H) Aliphatic [31] 1,326 δCH 2 bending vibration Cellulose and lignin [26] 1,382 δCH 2 bending vibration Aliphatic [31] 1,440 δ (CH 2 ) + δ (CH 3 ) Aliphatic [31] 1,455 δCH 2 bending vibration Aliphatic [31] 1,488 δ (CH 2 ) + δ (CH 3 ) Aliphatic [31] 1,527-1,551 ─C═C─ (in plane) Carotenoids [33,34] 1,601 ν(C─C) aromatic ring+σ (CH) Lignin [35,36] 1,630 C═C─C (ring) Lignin [35][36][37] intensities of all other bands in the spectra collected from leaves of CA and HLB + BL exhibited only very small variations compared with the spectra collected from leaves of HL trees.…”