15. Analytical Techniques:IR, NMR, Mass Spect

Identify each of the following compounds from its molecular formula and its IR and ¹H NMR spectra.

d. C₄H₈O₂

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Propose a structure for the following compound that fits the following ¹H NMR data: 

Formula:C₂H₄O₂                                            ¹H NMR:2.1 δ (singlet, 1.2 cm) 

                                                                                   11.5 δ (0.5 cm, D2O exchange)

Given the ¹H NMR spectrum and the molecular formula, suggest a structure for each molecule. [The IR spectrum suggests the presence of two C=O bonds.]

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Shown below is the ¹H NMR spectrum of the alkyl bromide used to make the phosphonium ylide that reacts with a ketone in a Wittig reaction to form a compound with molecular formula C₁₁H₁₄. What product is obtained from the Wittig reaction?

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A compound gives the following IR spectrum. Upon reaction with sodium borohydride followed by acidification, it forms the product with the ¹H NMR spectrum shown below. Identify the starting material and the product.

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The proton and ¹³C NMR spectra of a compound of formula C₄H₁₁N are shown here. Determine the structure of this amine, and give peak assignments for all of the protons in the structure.

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Identify each of the following compounds from its molecular formula and its IR and ¹H NMR spectra:

b.C₆H₁₄O

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Provide the structure of the unknown compound from the given information. 

Formula:C₄H₁₀O            IR:3200-3600 cm^{-1           1}H NMR:0.9 ppm (6H, doublet) 

                                                                                               1.8 ppm (1H, nonatet) 

                                                                                               2.4 ppm (1H, singlet) 

                                                                                               3.3 ppm (2H, doublet)

Provide the structure of the unknown compound from the given information. 

Formula:C₄H₉N              IR:2950 cm^-1, 3400 cm^{-1           1}H NMR:1.0 ppm (4H, triplet) 

                                                                                                         2.1 ppm (4H, triplet) 

                                                                                                         3.2 ppm (1H, singlet)

A compound of molecular formula C₈H₈O gives the IR and NMR spectra shown here. Propose a structure, and show how it is consistent with the observed absorptions.

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Propose a structure for the following compound that fits the following 1H NMR data: 

Formula:C₃H₈O₂                                                  ¹H NMR:3.36 δ (6H, singlet) 

                                                                                         4.57 δ (2H, singlet)

Show how you would distinguish among the following three compounds

(a) using infrared spectroscopy and no other information.

(b) using proton NMR spectroscopy and no other information.

(c) using ¹³C NMR, including DEPT, and no other information.

The spectral data below are presented in a manner similar to what you would find in a chemistry research journal. Identify the structure for each set of data.

(c) C₇H₁₄O₂ : ¹H NMR: δ 0.91 (3H, t, J = 7.0 Hz), 1.11 (6H, d, J = 7.0 Hz), 1.82 (2H, sextet), 2.40 (1H, sept, J = 7.0 Hz), 4.14 (2H, t, J = 7.1 Hz); IR (cm ⁻¹) : 1745, 1200

Identify each of the following compounds from its molecular formula and its IR and ¹H NMR spectra:

b. C₆H₁₂O₂

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Propose a structure for the following compound that fits the following ¹H NMR data: 

Formula:C₁₀H₁₄                                      ¹H NMR:1.2 ppm (6H, doublet) 

                                                                             2.3 ppm (3H, singlet) 

                                                                             2.9 ppm (1H, septet) 

                                                                             7.0 ppm (4H, doublet)