### 12.4 Which IR Spectrum is Consistent with an Alkene?Infrared (IR) spectroscopy is a powerful analytical technique used to identify functional groups in organic compounds. In this exercise, we aim to determine which IR spectrum corresponds to an alkene.Four IR spectra are presented, labeled (a), (b), (c), and (d). IR spectra display the transmittance (%) on the y-axis against the wavenumber (cm⁻¹) on the x-axis. The wavenumber is inversely proportional to the wavelength of the IR radiation absorbed by the sample; lower wavenumbers correspond to longer wavelengths and vice versa.#### Analysis of the IR Spectra:1. **Spectrum (a):** - Shows a broad absorption around 3300 cm⁻¹, which indicates the O-H stretching of an alcohol. - Contains additional absorptions around 1100 cm⁻¹, typical of C-O stretching vibrations.2. **Spectrum (b):** - Exhibits twin peaks near 2900 cm⁻¹, likely indicative of C-H stretches seen in alkanes. - There are no distinct peaks around 1600 cm⁻¹, which indicates the absence of C=C stretching.3. **Spectrum (c):** - Has a peak near 1650 cm⁻¹, which corresponds to the C=C stretching vibrations typical of an alkene group. - Also presents peaks near 3000 cm⁻¹, likely due to =C-H stretching of the alkene.4. **Spectrum (d):** - Displays a broad absorption around 3000-3500 cm⁻¹ and multiple strong absorptions around 1500-1600 cm⁻¹. - It shows characteristics of C=O stretching vibrations at around 1700 cm⁻¹.#### Conclusion:Based on the IR spectra analysis, spectrum (c) is consistent with an alkene. It shows a characteristic absorption peak around 1650 cm⁻¹, which is indicative of the C=C stretching vibrations commonly found in alkenes.Understanding these key absorption regions and their corresponding functional groups is essential for accurate organic compound identification using IR spectroscopy.

The main characteristic IR peak of alkene is a medium stretch in the range 3000 - 3100 cm-1 due to…

(a) (c) % Transmittance 12.4 Which IR spectrum is consistent with an alkene? 100 100 80 80 60 60- 40 40 20 20. 0. 4000 2500 2000 1500 1000 Wavenumber (cm¹) 3000 2500 2000 1500 Wavenumber (cm¹) 100 80 60- 40 20 % Transmittance 3500 0. 4000 3500 3000 1000 (b) (d) % Transmittance 0 4000 % Transmittance 3500 100 80 60 40 20 0 4000 3500 2000 Wavenumber (cm¹) 2000 Wavenumber (cm) 3000 2500 T 3000 2500 1500 1000 1000 1500

(a) (c) % Transmittance 12.4 Which IR spectrum is consistent with an alkene? 100 100 80 80 60 60- 40 40 20 20. 0. 4000 2500 2000 1500 1000 Wavenumber (cm¹) 3000 2500 2000 1500 Wavenumber (cm¹) 100 80 60- 40 20 % Transmittance 3500 0. 4000 3500 3000 1000 (b) (d) % Transmittance 0 4000 % Transmittance 3500 100 80 60 40 20 0 4000 3500 2000 Wavenumber (cm¹) 2000 Wavenumber (cm) 3000 2500 T 3000 2500 1500 1000 1000 1500

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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