00:01
Hello students, in this question we have to explain nmr spectrum of methyl butanoid.
00:05
So, methyl butanoid is an ester which will contain methyl group towards oxygen and butane group towards this carbon.
00:16
So, ch2 ch2 ch3 this will be the structure of methyl butanoid.
00:26
Now, let's draw the expected peaks in the nmr spectrum of methyl butanoid.
00:31
I am marking the different hydrogens as a, b, c and d.
00:37
Now, let's first write the signal of ha.
00:42
Ha is connected directly to oxygen.
00:46
So, this will be deshielded from 3 to 4 ppm value.
00:51
This will be the value of chemical shift.
00:53
If we have to identify the type of signal, we can see that there are no alpha hydrogens to this carbon atom because alpha position contains oxygen atom.
01:04
So, this will give simply a 3 hydrogen singlet.
01:08
Now, let's look at the signal of hb.
01:16
The protons of hb are directly linked to carbon that is adjacent to the carbonyl.
01:22
So, these signals will be very slightly deshielded at approximately 2 to 3 ppm.
01:30
And let's now judge the type of signal.
01:35
So, we can see that there are 2 hydrogen atoms present on the alpha carbon to this ch2 group.
01:43
So, the multiplicity will be 2 hydrogen triplet because we know that multiplicity of a signal is equal to n plus 1 where n is the number of hydrogens on adjacent carbons.
01:59
Now, let's judge the signal of hc.
02:05
Hc is directly connected to 2 carbon atoms.
02:09
So, it won't have the effect of electronegativity that much.
02:13
So, its signal will be highly shielded at about 1 to 2 ppm.
02:23
Now, this signal will be because of 2 hydrogens and its multiplicity can be calculated like this...