Related Experiment Video
Updated: May 18, 2026
19:58
Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
Published on: July 30, 2017
4-Nitro-1-[(trimethyl-sil-yl)ethyn-yl]benzene: low-temperature polymorph at 100 K
Jasmine N Millican1, Frank R Fronczek, Steve F Watkins
1Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804, USA.
Acta Crystallographica. Section E, Structure Reports Online
|September 13, 2012
Summary
This study reveals a low-temperature crystalline form of a silicon-containing compound. Upon cooling, its crystal structure changes, causing molecular distortions and volume reduction.
Area of Science:
- Crystallography
- Materials Science
- Chemical Physics
Background:
- The title compound, C(11)H(13)NO(2)Si, has a previously characterized room-temperature crystal structure.
- Understanding phase transitions in crystalline materials is crucial for predicting their properties.
Purpose of the Study:
- To investigate the low-temperature crystalline form of C(11)H(13)NO(2)Si.
- To characterize the structural changes and molecular distortions occurring upon cooling.
Main Methods:
- Single-crystal X-ray diffraction at low temperature (100 K).
- Analysis of crystallographic space group changes and unit cell volume.
- Determination of molecular geometry and atomic displacements.
Main Results:
- The crystal structure transitions from space group Pnma at 298 K to P2(1)2(1)2(1) at 100 K.
- A 5% decrease in unit cell volume was observed upon cooling.
- Significant molecular distortions occurred, with trimethyl-silyl and nitro groups rotating relative to the benzene plane.
- The crystal adopted an inversion twin structure at low temperature.
Conclusions:
- The compound exhibits a distinct low-temperature crystalline phase with altered symmetry and molecular conformation.
- Temperature-dependent structural analysis reveals significant changes in molecular packing and distortion.
- The formation of an inversion twin at low temperature adds complexity to the crystal structure.
Related Concept Videos
01:37NMR Spectroscopy of Benzene Derivatives
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling constants depend...
01:27Benzene to Phenol via Cumene: Hock Process
The synthesis of phenol from benzene via cumene and cumene hydroperoxide is called the Hock process. First, a Friedel–Crafts alkylation reaction of benzene with propene gives cumene. Then cumene forms cumene hydroperoxide via a radical chain reaction. In the chain initiation step, the benzylic hydrogen is abstracted to give a benzylic radical. In the chain propagation step, the benzylic radical reacts with an oxygen diradical to form a cumene hydroperoxide radical. The cumene hydroperoxide...
01:20Electrophilic Aromatic Substitution: Nitration of Benzene
The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the nitronium ion, which is linear in shape. The reaction occurs through the interaction of two strong acids, sulfuric and nitric acid.
01:26Polymer Classification: Stereospecificity
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
01:11Nomenclature of Aromatic Compounds with Multiple Substituents
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...
01:18Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism
Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of a single electron to the ring to form a benzene radical anion. This anion is highly basic—it abstracts a proton from the alcohol to form a cyclohexadienyl radical. Another single electron transfer gives the cyclohexadienyl anion. A proton transfer from the alcohol forms 1,4-cyclohexadiene. Since this reduction occurs via radical anion...