Alkene Stretching
Alkene Stretching - Related Videos
01:29
IR Frequency Region: Alkene and Carbonyl Stretching
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2024
Double bonds in alkenes and carbonyl compounds exhibit stretching frequencies in the diagnostic region of the IR spectrum. In addition, alkenes exhibit vinylic C–H stretching and C–H out-of-plane bending absorptions that are useful for identifying substitution patterns. Stretching frequencies are affected by several factors, such as resonance, inductive effects, ring strain, dipole moment, and hydrogen bonding. Consequently, the stretching frequency of the carbonyl double bond varies in...
06:52
Ozonolysis of Alkenes
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2023
Source: Vy M. Dong and Zhiwei Chen, Department of Chemistry, University of California, Irvine, CA This experiment will demonstrate an example of an ozonolysis reaction to synthesize vanillin from isoeugenol (Figure 1). Ozonolysis of alkenes, an oxidation reaction between ozone and an alkene, is a common method to prepare aldehydes, ketones, and carboxylic acids. This experiment also demonstrates the use of an ozone generator and a low temperature (−78 °C) reaction. Figure 1. Diagram showing...
07:42
Live Cell Imaging during Mechanical Stretch
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Cited by 12 •
2015
A novel imaging protocol was developed using a custom motor-driven mechanical actuator to allow the measurement of real time responses to mechanical strain in live cells. Relevant to mechanobiology, the system can apply strains up to 20% while allowing near real-time imaging with confocal or atomic force microscopy.
09:41
Stretching Micropatterned Cells on a PDMS Membrane
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Cited by 6 •
2014
This manuscript presents a technique to apply or release forces on adherent cells or tissues using unidirectional stretching.
11:46
Axon Stretch Growth: The Mechanotransduction of Neuronal Growth
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Cited by 30 •
2011
A unique tissue engineering method was developed to elongate numerous nerve fibers in culture by recapitulating axon stretch growth; a form of nervous system growth whereby nerves elongate in conjunction with growth of the enlarging body.
FAQs
The key requirement is a change in dipole moment during the vibration. Incident IR radiation is absorbed only when its frequency matches the vibrational frequency and the vibration produces that dipole change. Thus, the presence or intensity of a C=C band reflects both vibrational matching and how the molecular structure allows the interaction.
Molecular symmetry can reduce the observability of the signal. In highly symmetric alkenes, the C=C stretching absorption may be weak or absent, so failure to see a prominent band does not by itself exclude alkene functionality. This limitation makes structural interpretation dependent on additional absorptions and the molecule’s broader context.
An observed band should be interpreted alongside conjugation and substitution patterns rather than treated as an isolated label. The alkene stretching signal can help chemists assess these structural features, but the available information does not assign a unique frequency to each pattern. Combining the band with molecular context supports a more defensible structural conclusion.
A C=C stretching band near 1620–1680 cm⁻¹ is consistent with alkene functionality, but its position is not a complete structural assignment. Chemists use this interval as one piece of evidence, then compare it with other absorptions and the expected molecular context. This approach helps distinguish useful support from overinterpretation.
To apply alkene stretching in an IR-based analysis, first examine whether a signal occurs in the expected C=C region. Next, consider its strength, since highly symmetric structures can produce weak or absent absorptions. Finally, evaluate other absorptions and molecular context before using the result to support a proposed structure.
In organic synthesis, the signal can provide evidence that alkene functionality is present in a material being examined. In analytical research, it contributes to structure determination when interpreted with the rest of the IR data and molecular context. Its value is therefore confirmatory and comparative, rather than a standalone identification.