Please explain which compound is optically active-
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This structure has no centre of symmetry or plane of syymmetry so it is optically active.
Take a point in the centre and draw lines meeting atoms at the corner.Are you getting same chemical environment in all directions -NO
Draw planes from the edges of cylobutane and you can see you are not getting exactly same reflection on the both sides of the plane.
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This molecule has plane of symmetry because if you draw a line through the centre of two chlorine atoms bond, you can see identical mirror images on both sides.
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None of the carbon is asymmetric because every carbon is the part of symmetric cyclohexane ring.
Circled carbon is also bonded to same groups if you check clockwise or anticlock wise.
sp2 carbon of double bonds can not show optical isomers.
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This structure has plane of syymmetry (meso)so it is optically inactive.
Take a point in the centre and draw lines meeting atoms at the corner.Are you getting same chemical environment in all directions -yes
Draw planes from the corners of cylobutane and you can see you are getting exactly same reflection on the both sides of the plane.
Compounds with plane of symmetry and achiral centre are called as meso compounds.These compounds have aymmetric centres but still optically inactive due to plane of symmetry.