Question

Having trouble figuring out these two unknown compounds. 17) Formula: C8H10O with a strong peak at 3200 cm^-1

17) Chemical Formulac: CHroO IR: strong broad peak at 3200 cm-1 Singlet, 3 Triplet, 1H Singlet, 2hH Doublet, 1H Singlet, 1H Singlet, 1H Doublet, 1H 0 2 6 PPM 18) Chemical Formula: C10H13Br Doublet, 3H Doublet, 2H Triplet, 3hH Quartet, 2H Doublet, 2H Quartet 1H 4 PPM

18) Formula: C10H13Br I just need to know the structures of each of them if you could please help me out!

Answer 1

Answer 17

IR peak at 3200 cm^-1 indicates the presence of -OH group

As per proton NMR spectra, the structure is

CH3 Spectral details are as below: singlet, 1H at~5.2 ppm singlet, 1H at 4.6 ppnm HO CH2 doublet, 1H at 7.4 ppm singlet, 1H at 7.25 ppm CH3 triplet, 1H at 7.5 ppm singlet, 1H at 2.3 ppm doublet, 1H at 7.1 ppm Molecular formula C^HigO

The groups i.e. CH₃ and CH₂OH are meta to each other.

Spin multiplicity i.e. singlet, doublet etc is by number of protons on adjacent carbons + 1.

For example, -CH₃ group has no proton on its adjacent carbon, so it appears as singlet

This is not true for protons linked to heteroatoms i.e. O, N etc. So, -OH group appears as singlet even though -CH₂ adjacent to it has 2 protons.

Similarly, -CH₂ group has no proton on its adjacent carbon, so it appears as singlet.

All the protons along with the spectral data have been indicated in the figure above.

Answer 18

The structure is

H2C CH Br Spectral details are as below: triplet, 3H at 1.3 ppm quartet, 2H at 2.75 ppm н.с Both blue marked protons doublet, 2H at7.1 ppm Both red marked protons doublet, 2H at~7.25 ppm CH Br CH3 doublet, 3H at ~2.1 ppm quartet, 1H at-5.1 ppm Molecular formula C10H13Br

The structure is symmetric as both red marked and blue marked protons appear at same ppm value

The doublet for red protons is at higher value because they are closer to Br atom than the blue marked ones. Presence of Br decreases electron density and hence protons are deshielded resulting in higher ppm value.