Vibrational spectra and structure of esters—I. Infrared and Raman spectra of CH3COOCH3, CH3COOCD3, CD3COOCH3 and CD3COOCD3

George, W. O.; Houston, Tracey; Harris, William M.

doi:10.1016/0584-8539(74)80020-6

Cited by 64 publications

(33 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…57 These observations are consistent with the relative IR peak intensities of methyl acetate vibrations obtained both experimentally and using normal-mode analysis. 56,58 For PMMA, α-methyl groups are not directly connected to the carbonyl groups; however, the bridging atom, a quaternary carbon, could still pass on the electron-withdrawing effects to the nearby α-methyl and methylene groups, which reduces the dipole derivative of the symmetric vibration of α-methyl and methylene groups. 57 Using our ab initio results, we have calculated the molecular hyperpolarizability tensor for methylene, α-methyl, and estermethyl groups.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

et al. 2014

View full text Add to dashboard Cite

The chemical composition and molecular structure of polymeric surfaces are important in understanding wetting, adhesion, and friction. Here, we combine interfacesensitive sum frequency generation spectroscopy (SFG), allatom molecular dynamics (MD) simulations, and ab initio calculations to understand the composition and the orientation of chemical groups on poly(methyl methacrylate) (PMMA) surface as a function of tacticity and temperature. The SFG spectral features for isotactic and syndiotactic PMMA surfaces are similar, and the dominant peak in the spectra corresponds to the ester-methyl groups. The SFG spectra for solid and melt states are very similar for both syndiotactic and isotactic PMMA. In comparison, the MD simulation results show that both the ester-methyl and the α-methyl groups of syndiotactic-PMMA are ordered and tilted toward the surface normal. For the isotactic-PMMA, the α-methyl groups are less ordered compared to their ester-methyl groups. The backbone methylene groups have a broad angular distribution and are disordered, independent of tacticity and temperature. We have compared the SFG results with theoretical spectra calculated using MD simulations and ab initio calculations. Our analysis shows that the weaker intensity of α-methyl groups in SFG spectra is due to a combination of smaller molecular hyperpolarizability, lower ordering, and lower surface number density. This work highlights the importance of combining SFG spectroscopy with MD simulations and ab initio calculations in understanding polymer surfaces. ■ INTRODUCTIONOne of the simplest and still commonly used technique to characterize surfaces of polymers is the measurement of water contact angle. Although this is a very simple technique to judge the wettability of surfaces, it lacks molecular level sensitivity to identify the chemical composition and molecular structure of surfaces. In addition, the rearrangement of molecules at the surface after exposure to water complicates the interpretation of contact angle results. 1 X-ray photoelectron spectroscopy (XPS), a vacuum-based technique, provides excellent information regarding the elemental composition present at the surfaces. However, to identify different hydrocarbon groups (or bondings) is not trivial and relies on subtle shifts of carbon binding energies in the high-resolution XPS analysis. 2 Attenuated-total-reflectance infrared can be used to pick up molecular fingerprints, but this technique samples a much thicker layer than the surface region that affects wetting, surface energy, and friction. 3 In the past two decades, surface-sensitive infrared−visible sum frequency generation spectroscopy (SFG) has been used to study polymer surfaces, 4−7 polymer/liquid interfaces, 7−11 polymer/metal or metal oxide interfaces, 5,12−15 and polymer/polymer interfaces. 12,16−19 SFG is a second-order nonlinear optical technique, and under electric dipole approximation, the SFG signal is only generated by the ordered molecules at surfaces or interfaces and the contribution from ...

show abstract

Section: ■ Results and Discussionmentioning

confidence: 99%

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Calculated frequencies of cis-MeOAc are compared with gas phase experimental data from George et al 8 and Shimanouchi. 5 Five modes are predicted to lie below 500 cm −1 , three out-of-plane vibrations, the C-CH 3 torsion (ν 27 ), the O-CH 3 torsion (ν 26 ), the C-O single bond torsion (ν 25 ), and two in-plane bending modes ν 17 (COC bending) and ν 16 In gas phase, experimental data are available for only three low frequency modes: the two bending modes ν 16 and ν 17 and the ν 25 torsion.…”

Section: Full Dimensional Anharmonic Analysismentioning

confidence: 99%

“…2 From 1956, the gas phase infrared and microwave spectra of methyl acetate have been measured. [4][5][6][7][8][9][10] Structure and a) Author to whom correspondence should be addressed. Electronic mail: senent@iem.cfmac.csic.es.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5][6][7][8][9][10][11] Although, methyl acetate has not been already detected in astrophysical sources, new spectroscopic studies have been motivated by the setup of new radioastronomical observatories. 3 The presence of MeOAc in gas phase astrophysical sources was postulated because related molecules such as methyl formate, acetic acid, and many other organic compounds containing methyl groups are listed as astrochemical species.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Highly correlated ab initio study of the far infrared spectra of methyl acetate

Senent

Domı́nguez-Gómez

Carvajal

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

Highly correlated ab initio calculations (CCSD(T)) are used to compute gas phase spectroscopic parameters of three isotopologues of the methyl acetate (CH 3 COOCH 3 , CD 3 COOCH 3 , and CH 3 COOCD 3 ), searching to help experimental assignments and astrophysical detections. The molecule shows two conformers cis and trans separated by a barrier of 4457 cm −1 . The potential energy surface presents 18 minima that intertransform through three internal rotation motions. To analyze the far infrared spectrum at low temperatures, a three-dimensional Hamiltonian is solved variationally. The two methyl torsion barriers are calculated to be 99.2 cm −1 (C-CH 3 ) and 413.1 cm

show abstract

“…The Raman band at 844 cm-' has been assigned to the C-C symmetric stretching mode (12,13). A second band at 864 cm-' increases in intensity as the concentration of solute increases.TheRamanbandatabout 1740cm-'hasbeenassigned to the C=O stretching vibration (12)(13)(14). A shoulder at 1720 cm-' also increases with the increase of concentration of solute.…”

Section: Introductionmentioning

confidence: 99%

A Raman spectral study of solvation and ion association in the systems LiAsF₆/CH₃CO₂CH₃ and LiAsF₆/HCO₂CH₃

Deng¹,

Irish²

1991

Can. J. Chem.

View full text Add to dashboard Cite

ZHONGYI DENG and DONALD E. IRISH. Can. J. Chem. 69, 1766 (1991).The structure of the solvated lithium cation in methyl acetate (MA) solutions has been investigated using Raman spectroscopy. Two bands at 844 and 864 cm-' have been assigned to two different types of MA: the former is from the bulk solvent and the latter arises from MA molecules solvating the lithium cation. From measurement of changes in intensity of these bands with increasing salt concentration a solvation number of four for Li+ in MA has been inferred. Changes in the Raman bands at ca. 1740 cm-' suggest that solvation occurs through the carbonyl group. Evidence for contact ion pairing between Li'and AsF; is also presented. An equilibrium between solvent-shared ion pairs and contact ion pairs is proposed for which an equilibrium constant is estimated. The system LiAsF,Imethyl formate (MF) is similar in structure.Key words: Raman, ion pair formation, lithium and hexafluoroarsenate ions, methyl acetate and formate, lithium ion solvation. IntroductionThe search for new electrolyte-solvent systems capable of providing improved performance of both primary and secondary lithium cells and batteries is ongoing. Aprotic solvents, such as ethers, esters, amides carbonates, nitriles, and dimethyl sulfoxide, either alone or mixed, have received extensive study (1). Effort has been focused on overcoming the inferior conductivity of the electrolyte, relative to aqueous systems. Recently methyl formate (MF) and methyl acetate (MA) were identified as possible solvents (2-5). Conductance measurements (3-5) and, for MAILiAsF, and MALiClO,, microwave relaxation spectroscopy and some infrared spectra (5) have been reported. Solutions of MA have a surprisingly high conductance over a wide temperature range. Despite evidence for ion pairing, strong ion-solvent interactions were also suggested in these studies.Raman spectroscopy has proved to be a powerful technique for probing ion-ion and ion-solvent interactions. Recently Hyodo and Okabayashi studied local structure in LiClO,/EC (ethylene carbonate) and mixed solvent systems (6). We have reported Li' solvation in CH,CN solutions, and adsorption of the species at silver electrode surfaces (7). In anticipation of surface

show abstract

Vibrational spectra and structure of esters—I. Infrared and Raman spectra of CH3COOCH3, CH3COOCD3, CD3COOCH3 and CD3COOCD3

Cited by 64 publications

References 17 publications

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

Highly correlated ab initio study of the far infrared spectra of methyl acetate

A Raman spectral study of solvation and ion association in the systems LiAsF₆/CH₃CO₂CH₃ and LiAsF₆/HCO₂CH₃

Contact Info

Product

Resources

About

Vibrational spectra and structure of esters—I. Infrared and Raman spectra of CH3COOCH3, CH3COOCD3, CD3COOCH3 and CD3COOCD3

Cited by 64 publications

References 17 publications

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

Molecular Structure of Poly(methyl methacrylate) Surface. I. Combination of Interface-Sensitive Infrared–Visible Sum Frequency Generation, Molecular Dynamics Simulations, and ab Initio Calculations

Highly correlated ab initio study of the far infrared spectra of methyl acetate

A Raman spectral study of solvation and ion association in the systems LiAsF6/CH3CO2CH3 and LiAsF6/HCO2CH3

Contact Info

Product

Resources

About

A Raman spectral study of solvation and ion association in the systems LiAsF₆/CH₃CO₂CH₃ and LiAsF₆/HCO₂CH₃