Conclusions 1. Does your IR spectrum support the structure of the product? Expla

Question

Conclusions 1. Does your IR spectrum support the structure of the product? Explain; refer to the exact IR band or bands you are using to reach this conclusion. 2. Is the product the Z- or E-isomer? Give the experimental evidence, using both of the following: a. The Z- isomer has been reported to melt at 107-1080 and the E- at 130-1320 b. In the 1H NMR, vinylic protons that are cis to one another have a pling constant (J-value) of 6-15 Hz (Hertz), while those that are trans to one another have J = 1 1-18 Hz.

Explanation / Answer

Interpretation of IR spectrum,

1. The IR spectrum shows,

Peak around 3000-3100 cm-1 for the sp2 =C-H stretch and peak at around 1670 cm-1 corresponding to the carbonyl sp2 C=C stretching. So the compound has an alkenic group.

The other peaks are for C-C and C-H single bonds.

The IR thus supports presence of alkenic double bond.

2. The geometry of the compound,

a. The isomer would thus melt at lower temperature.

b. Looking at the NMR, we get,

coupling constant (J) = 3183 - 3173 = 10 Hz

Which corresponds to the cis configuration for the vinylic protons

Therefore the compound here is having a cis configuration as seen by NMR spectrum.

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