Part 8: SPECTROSCOPY

The following data is available from the question:

MS: M =   114 g/mol (even, no isotope pattern for Cl or Br)

EA: Calculates empirical formula = C3H5O (IR confirms O is present).
Which with MW from MS gives molecular formula = C6H10O2 .  From here we get the IHD = 2

IR: There are significant absorptions at 1720cm-1 due to a C=O and at 1640cm-1 due to a C=C, C-O possible due to bands between 1200 and 1100cm-1. There is no OH (about 3500cm-1).

13C nmr: The proton decoupled spectrum shows a total of 6 peaks indicating 6 types of C. By analysis of the chemical shifts, we have a C=O (probably an acid derivative) at 167 ppm, 2 types in the region 125-140 ppm is C=C, 61 ppm is typical of a C-O and those at 18 and 14 ppm are most likely from hydrocarbon portions.

1H nmr: First of all we have 5 types of H showing up. After this, it's a good idea to tabulate the information to make sure you get it all correctly matched up:
 

d/ppm
multiplicity
integration
Inference
6.1
"multiplet"
1
C=C-H
5.5
"multiplet"
1
C=C-H
4.2
quartet
2
CH2 coupled to 3H, deshielded by O ?
1.9
singlet
3
CH3 with no adjacent H, slightly deshielded
1.3
triplet
3
CH3 coupled to 2H

The most significant structural information in the H nmr data is that we have an disubstituted alkene (note that the MW, MF, number of ArH all rule out the it being an benzene system), an ethyl group : -CH2-CH3 most likely as an ethoxy group: -O-CH2-CH3 and an isolated methyl group : -CH3

Summary....
The MS indicated MW =  114 g/mol.
The IR showed the presence of  C=O, C=C and C-O bonds.
13C peak at 167 ppm suggests that the C=O is a carboxylic acid derivative
H nmr also gives a disubstituted alkene, a -O-CH2-CH3 and an uncoupled  -CH3.
Use this to check the molecular formula : C6H10O2 = 6 x 12 + 10 x 1 + 2 x 16 = 114 g/mol
So with all this information we have the following pieces: C=O, -O-CH2-CH3, -CH3 and H-C=C-H or H2C=C.

Altogether...
 

With the pieces we have :  C=O, -O-CH2-CH3, -CH3 and H-C=C-H or H2C=C.
IR and 13C suggest an ester so we have : CO2CH2-CH3
This means the two substituents on the alkene C=C are the ester group and the -CH3
There are three possible arrangements: 1,1- , cis-1,2- or trans-1,2-
If it were 1,2- then the methyl group would have to have an H neighbour and therefore appear as a doublet (i.e. in a CH3-CH= system).
Therefore, it must be the 1,1-isomer where is has no adjacent H.....
ethyl methacrylate
ethyl methacrylate
or
ethyl 2-methylpropenoate

The final step should always be to check what you have drawn. The easiest thing to check is usually the coupling patterns you would expect to see, and the chemical shifts of each unit.
You should be asking yourself : "Does my answer give me what the H-nmr shows ?"