Among these compounds first four are aromatic where fifth compound is not aromatic.
Coming to the first compound we have three π-bonds and a vacant orbital on B. So there are 6 electrons in conjugation and it obeys Hückel's rule. Hence, it is aromatic.
Here we have two π-bonds and a lone pair on N. So there are six electrons in conjugation and hence, it is aromatic. Note: Lone pair on right nitrogen is not involved in conjugation.
Similar to 1 and 2, we have a vacant orbital on B, a lone pair on N and two π-bonds. So totally there are six electrons in conjugation and hence, it is aromatic.
Form the following image you can understand why 4th compound is aromatic. Since there are six electrons in delocalisation where four electrons are from two π-bonds and two electrons from oxygen's lone pair.
I hope you can understand why 5th compound is not aromatic as it does not obey Hückel's rule.
Among these compounds first four are aromatic where fifth compound is not aromatic.
Coming to the first compound we have three π-bonds and a vacant orbital on B. So there are 6 electrons in conjugation and it obeys Hückel's rule. Hence, it is aromatic.
Here we have two π-bonds and a lone pair on N. So there are six electrons in conjugation and hence, it is aromatic. Note: Lone pair on right nitrogen is not involved in conjugation.
Similar to 1 and 2, we have a vacant orbital on B, a lone pair on N and two π-bonds. So totally there are six electrons in conjugation and hence, it is aromatic.
Form the following image you can understand why 4th compound is aromatic. Since there are six electrons in delocalisation where four electrons are from two π-bonds and two electrons from oxygen's lone pair.
I hope you can understand why 5th compound is not aromatic as it does not obey Hückel's rule.
Among these compounds first four are aromatic where fifth compound is not aromatic.
Note: Lone pair on right nitrogen is not involved in conjugation.
I hope you can understand why 5th compound is not aromatic as it does not obey Hückel's rule.
Among these compounds first four are aromatic where fifth compound is not aromatic.
Note: Lone pair on right nitrogen is not involved in conjugation.
I hope you can understand why 5th compound is not aromatic as it does not obey Hückel's rule.
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