How many ^1 H NMR signals would you expect from each of the...

Key Concepts

Magnetic Equivalence

Magnetic equivalence extends beyond basic chemical equivalence, considering the spin-spin interactions between protons. Protons that are both chemically and magnetically equivalent will have the same NMR signal without coupling differences, which is important in accurately counting the number of signals in a spectrum.

Proton NMR Spectroscopy

Proton (¹H) NMR spectroscopy is a technique that detects the environments of hydrogen atoms in a molecule. It provides information about the number of chemically distinct hydrogen environments present by displaying separate signals for protons in different electronic surroundings.

Chemical Equivalence

Chemical equivalence refers to a group of protons that have identical electronic environments within a molecule. Protons that are chemically equivalent give rise to a single NMR signal, as they experience the same magnetic field and chemical shift.

Molecular Symmetry

Molecular symmetry plays a crucial role in determining proton equivalence. Symmetry elements, such as mirror planes or rotational axes, can make otherwise different protons equivalent, thus reducing the number of unique NMR signals observed.

Transcript

00:01 This problem, the number of nmr signal for each of the given compound is to be found.

00:11 Protones appear depending on the environment in which they are in the nmr spectrum.

00:22 When the protons are in identical environment, they appear at the same delta value in nmr.

00:30 So that is what we have to identify the identical protons.

00:33 Here the first molecule is butane a cs3 here sch2 here ch2 here ch2 and cs3 so these two cst3 cylindrical these two ch2 cylindrical so you get two signals second combo it's ethanol ch3 ch2 and oh so you expect three signals for this propine it is ch3 cx3 cx and two hydrogens see here these two hydrants are two in two different environment they are not identical one is cis and the other is strands to the me like so you expect to warn a b c and d four types of protons so we get four types of protons here now this molecule the next one we have here this this molecule is symmetric.

01:50 You can see the symmetry here and here so they will give identical peak.

01:54 And here the cs3 group will see h3 will also give same identical peak.

02:01 So you get two sets of protons.

02:07 So two different animal signals will be observed.

02:12 This module we have h here and h here and h here.

02:24 And the cht and see here these two are these two problems are high zero topic because here you have we have a symmetric carbon so we expect this molecule to be the asthenotypic so we'll get one a b c and d there will be four types of protons and four signals will be observed here the ch3, the two cs3 groups are identical because it is having a symmetry here and ch2 here and ch2 here.

03:18 So two such a protons, so both are a and b, so two signals.

03:30 Here there are two hydrogens here and cs3 here and we have two hydrogens here.

03:40 Since the hydrogens are trans from these two carbons these two hydrants are trans from these two carbons this you have a hydrant so each of this hydrogen is in a same environment and these two hydrants also if this hydrogen is cyst to this metal group these two are cis very similarly these two are also cis you can say this on the back side and this on the front side so you will get three sets of protons which is a this is b and none of the mecc.

04:35 So we will get three signals while in the cis molecule you can be seen you can see here these two hydrogens are on the bottom side and one of the hydrogen is cyst to the methyl tube both the metallurts and the other hydrogen is trans so there will be there in two different and environment and hence we expect this molecule to show 1, 2, 3 and 4 signals.

05:19 Now this molecule we have h, h, c .h, c .h, c .h2, c .h.

05:32 So these hydrants are entirely different...

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