Data ArticleEnergy profile, structure, spectroscopic and quantum chemical investigations of trans–3,4–(methylenedioxy)cinnamic acid
Graphical abstract
Section snippets
Rationale
Cinnamic acid derivatives are used in the Shikimic acid (3,4,5–trihydroxycyclohex–1–ene–1–carboxylic acid) metabolic pathways of higher plants [1]. Cinnamic acid is used in flavors, synthetic indigo and certain pharmaceuticals. A major use is in the manufacturing of the methyl, ethyl and benzyl esters for the perfume industry [2]. Cinnamic acid is used as a precursor to the sweetener aspartame via enzyme–catalysed amination to phenylalanine [3]. The cinnamic acid derivatives are used as
Materials and methods
The compound trans–3,4–(methylenedioxy)cinnamic acid (MDCA) was obtained from Aldrich Chemicals, U.S.A and used as such to record FT–IR and FT–Raman spectra. The FT–IR spectrum of the compound is recorded by KBr pellet method on a Bruker IFS 66 V spectrometer equipped with a Globar source, Ge/KBr beam splitter and a TGS detector in the range of 4000–400 cm–1. The spectral resolution is 2 cm–1. The FT–Raman spectrum of the compound is also recorded in the range 4000 to 100 cm–1 using the same
Conformational analysis
The conformational analysis is carried out by potential surface scan with B3LYP method using 6–31G** basis set in order to ascertain the most stable geometry. The energy profile as a function of angle of rotation with respect to the dihedral angle C7–C8–C9–O10 is shown in Fig. 1. All the possible conformers are optimised to find out the energetically and thermodynamically more stable configuration of the compound. The compound MDCA has three different conformers. The possible conformers of the
Analysis of molecular electrostatic potential
Total electron density surface mapped with molecular electrostatic potential of MDCA determined by B3LYP/6–311++G** method is shown in Fig. 4. This surface displays the molecular shape, size and reactive sites. In the total electron density mapped with the electrostatic potential surface the red colour indicates the high negative charge; blue colour reflects positive charge; the slightly electron deficient region is represented by light blue colour; slightly electron rich region is shown by
Frontier molecular orbital analysis
The energies of HOMO, LUMO, LUMO+1 and HOMO–1 and LUMO–HOMO the orbital energy gap are calculated by B3LYP/cc-pVTZ method. The illustration of molecular orbitals and their respective positive and negative regions are shown in the supplementary Fig. S3. The positive and negative phases are represented in red and green colour, respectively. From the plots one can see that the region of HOMO and LUMO levels spread over the entire molecule and the calculated energy gap of LUMO–HOMO explains the
Natural bond orbital analysis
The atomic charges, atomic orbital occupancies and their parent and atomic hybrid contribution to the bonds and donor–acceptor interactions are evaluated by NBO analysis. Supplementary Table S2 depicts the bonding concepts such as type of bond orbital, their occupancies, the natural atomic hybrids of which the NBO is composed, giving the percentage of the NBO on each hybrid, the atom label, and hybrid label showing the hybrid orbital (spx) composition (the amount of s–character, p–character,
Vibrational analysis
The observed FT–IR and FT–Raman spectra of MDCA are shown in Fig. 5. The observed and calculated frequencies using B3LYP/6–311++G** and B3LYP/cc–pVTZ methods along with their relative intensities, probable assignments are summarised in Table 3. The molecule possesess CS point group symmetry. The 60 modes of vibrations are distributed into Гvib = 41A' + 19A". All are active in both infrared and Raman spectra. The vibrational assignments of all the fundamental modes are also supported by
NMR spectral investigations
The 13C and 1H NMR chemical shifts of the title compound have been determined by GIAO method using B3LYP functional with cc–pVTZ basis set. The 1H and 13C theoretical and experimental chemical shifts, isotropic shielding constants and the assignments of MDCA are presented in Table 4. The observed 1H and 13C NMR spectra of the compound in DMSO–d6 solvent are given in the Fig. 6, Fig. 7.
Unsaturated and aromatic carbons normally found with chemical shift values from 100 to 200 ppm [48], [49], [50]
Structure–activity relations
The atomic charges of MDCA calculated by NBO analysis using the B3LYP method with cc–pVTZ basis set is presented in Table 5. The carbon atoms C3, C4 and C9, C14 have positive charge while other atoms have negative charge. The positive charge of C1 indicates the delocalization C7C8 π– electron towards the CO group. The very high positive charge on the carbon C9 is due to the partial polar nature of C=O group. The correlation of atomic charges of 3,4–(methylenedioxy)cinnamic acid is given in the
Conclusions
The molecular structural parameters and thermodynamic properties of trans–3,4–(methylenedioxy)cinnamic acid (MDCA) have been determined by B3LYP method with 6–311++G** and cc–pVTZ basis sets. The vibrational frequencies of the fundamental modes of the compound have been precisely assigned, analysed and the theoretical results were compared with FT-IR and FT-Raman data. The energies of frontier molecular orbitals of the compound are also evaluated. The orbital energy gap (ELUMO–EHOMO) is
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Crdiet author statement
V. Arjunan: Conceptualisation; Methodology; Data curation; Visualisation; Investigation; Reviewing and Editing, computational analysis.
L. Devi: Data curation; writing, revieweing and editing, data evidence collection.
S. Mohan: Software, Reviewing and editing.
References (52)
- et al.
J. Mol. Struct.
(2005) - et al.
Food Res. Int.
(2012) - et al.
J. Mol. Struct.
(2007) - et al.
J. Mol. Struct.
(2006) - et al.
J. Mol. Struct.
(2015) - et al.
J. Mol. Struct.
(2016) - et al.
Chem. Data Collect.
(2018) - et al.
Tetrahedran
(1975) - et al.
Spectrochim. Acta
(2004) - et al.
Anly.Chim. Acta
(2007)