Local Order-Disorder Transition Driving by Structural Heterogeneity in a Benzyl Functionalized Ionic Liquid
Luiz F O Faria1, Vitor H Paschoal1, Thamires A Lima1
1Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo , Avenida Prof. Lineu Prestes 748, 05508-000, São Paulo, São Paulo, Brazil.
The Journal of Physical Chemistry. B
|October 3, 2017
Summary
A local order-disorder transition in ionic liquid [Bzmim][N(CN)2] was observed. Spectroscopic and simulation data reveal this transition originates from structural rearrangements in the benzyl group.
Area of Science:
- Materials Science
- Physical Chemistry
- Chemical Physics
Background:
- Ionic liquids (ILs) exhibit complex thermophysical behavior.
- Understanding the microscopic origins of thermal events in ILs is crucial for their application.
- 1-benzyl-3-methylimidazolium dicyanamide, [Bzmim][N(CN)2], is a low-viscosity ionic liquid with potential applications.
Purpose of the Study:
- To investigate the local order-disorder transition in [Bzmim][N(CN)2].
- To elucidate the microscopic origin of this transition using spectroscopic and computational methods.
- To correlate the observed transition with the ionic liquid's structural heterogeneity and glass-forming ability.
Main Methods:
- Differential scanning calorimetry (DSC) and specific heat measurements.
- Molecular dynamic (MD) simulations.
- X-ray diffraction (XRD) measurements.
- Raman and Nuclear Magnetic Resonance (NMR) spectroscopy at variable temperatures.
Main Results:
- A thermal event was detected between 250-260 K, characterized by small enthalpy variation, distinct from melting or crystallization.
- MD simulations and XRD suggested domain segregation within the liquid structure.
- Spectroscopic analyses identified structural rearrangements involving the benzyl group as the microscopic cause of the thermal event.
- The structural heterogeneity and domain rearrangements contribute to the good glass-forming ability of [Bzmim][N(CN)2].
Conclusions:
- The study reveals a local order-disorder transition in [Bzmim][N(CN)2] driven by benzyl group rearrangements.
- This transition is linked to the liquid's inherent structural heterogeneity and domain dynamics.
- The findings enhance the understanding of complex thermal phenomena in ionic liquids and their implications for glass formation.
Related Concept Videos
01:18Directing and Steric Effects in Disubstituted Benzene Derivatives
4.2K
When disubstituted benzenes undergo electrophilic substitution, the product distribution depends on the directing effect of both substituents. When the directing effects of both substituents reinforce each other, a single product is obtained. For example, bromination of p-nitrotoluene occurs ortho to the methyl group and meta to the nitro group, which is the same position, resulting in a single product. However, if the directing effects of the two groups oppose each other, the...
4.2K
01:15Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene
11.9K
Chlorination and bromination are important classes of electrophilic aromatic substitutions, where benzene reacts with chlorine or bromine in the presence of a Lewis acid catalyst to give halogenated substitution products. A Lewis acid such as aluminium chloride or ferric chloride catalyzes the chlorination, and ferric bromide catalyzes the bromination reactions. During the bromination of alkenes, bromine polarizes and becomes electrophilic. However, in the bromination of benzene, the bromine...
11.9K
03:51Molecular Orbital Theory II
27.8K
Molecular Orbital Energy Diagrams
27.8K
01:13Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
7.6K
Bromination and chlorination of aromatic rings by electrophilic aromatic substitution reactions are easily achieved, but fluorination and iodination are difficult to achieve. Fluorine is so reactive that its reaction with benzene is difficult to control, resulting in poor yields of monofluoroaromatic products. To address this, Selectfluor reagent is used as a fluorine source in which a fluorine atom is bonded to a positively charged nitrogen.
7.6K
01:18Structure of Benzene: Molecular Orbital Model
13.0K
According to the molecular orbital (MO) model, benzene has a planar structure with a regular hexagon of six sp2 hybridized carbons. As shown in Figure 1, each carbon is bonded to three other atoms with C–C–C and H–C–C bond angles of 120°. The C–H bond length is 109 pm, and the C–C bond length is 139 pm which is midway between the single bond length of sp3 hybridized carbons (154 pm) and sp2 hybridized carbons (133 pm).
13.0K
01:11Nomenclature of Aromatic Compounds with Multiple Substituents
10.8K
When more than one substituent is present on the benzene ring, the IUPAC nomenclature depends on the number of substituents present.
For disubstituted benzene derivatives, with two groups attached to the benzene ring, three constitutional isomers are possible. For example, consider dimethyl benzene, often called xylene, where the second methyl group can be substituted at the second, third, or fourth carbon. The relative position of the substituents is represented by prefixes ortho, meta, or...
For disubstituted benzene derivatives, with two groups attached to the benzene ring, three constitutional isomers are possible. For example, consider dimethyl benzene, often called xylene, where the second methyl group can be substituted at the second, third, or fourth carbon. The relative position of the substituents is represented by prefixes ortho, meta, or...
10.8K