Chapter 16.11, Problem 27PTS

7. Consider the C=O stretching data for the following cyclic ketones: cyclopropane 1813 cm³¹; cyclobutanone 1791 cm³¹; cyclopentanone 1740 cm³¹. (a) which ketone has the strongest bond? (b) where in the trend would you expect the C=O stretch of cyclopropenone? (Use the hybridization information in the same way we used hybridization for C-H stretching.)

What are the possible electronic excitations in the below compounds? (i) (ii) (iii) (iv) Provide the energy level diagrams. Explicate which excitations are observable and which of them are not observable in the UV-Visible spectrum. Methane 1,3-butadiene Pyrrole Furan

The infrared absorption spectrum of 12C14N has its strongest band at 2500 cm-1 wavenumber. Calculate the force constant (N/m) of the bond in this molecule.

Given that Kb for (CH3)3N is 6.3 × 10-5 at 25 °C, what is the value of Ka for (CH3)3NH at 25 °C?

The experimental wavenumber of single (C-C) and double (C=C) carbon-carbon bonds are 1430 cm-¹ and 1675 cm-¹, respectively. Assuming HO model for the bonds, compare their: a) bond strengths, k b) zero-point vibrational energy, Eo

20) An unknown compound has the chemical formula CH₂O. It's IR spectrum and ¹H NMR spectrum are shown below. Propose a structure for the unknown molecule. Calculate the Degrees of Unsaturation (DU), assign any important peaks in the IR spectrum to vibrational modes and briefly explain why the structure fits the 'H NMR spectrum that is provided Degrees of unsaturation (show work below): 442 Du= (2(3)+2)-6 2 -8-16 - 2²/2/2 = 1 3437 1739 Amply 0 Vibrational Assignments of IR Peaks Wavenumber (cm-¹) Vibrational Assignment 0-4 stretch 6=0 strekh Peak 1: 9.79 ppm 14 Singlet 3 8 Brief rationalization for proposed structure: (explain why DU, IR, and NMR are consistent with proposed structure) ppm Peak 2 2.45 ppm 2H Quartet Peak 3 1.11 ppm 3H Triplet D Proposed structure of unknown:

An infrared spectrum of a mixture of methyl amine, CH3−NH2, and methylene imine, CH2=NH2, displayed absorptions at 1050 and 1640 cm−1cm−1, among others. Which of these two absorptions would you expect belongs to the C−N and which to the C=N stretch?

[1,3] Sigmatropic migrations of hydrogen cannot occur under thermal conditions, but [1,3] sigmatropic migrations of carbon can occur under thermal conditions. Explain!

Identify the two geometric isomers of stilbene C6H5CH=CHC6H5 from their λmax values 294 and 278 nm. Explain your answer.