Home > Community > Are monosubstituted cyclopropanes achiral or chiral?
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Michael Flynn

Are monosubstituted cyclopropanes achiral or chiral?

Dami Victor  Follow

Here is a 3-D conformer from PubChem

enter image description here

As you can clearly see, a plane of symmetry can be sent along the black line perpendicular to the plane of the screen. Hence, the molecule is achiral. If you take a mirror image, you can ultimately super-impose it again on the parent form

Here is an illustrative 3D image(courtesy of andselisk) which clearly shows the plane of symmetry in pink and ring plane in blue.

enter image description here

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David Thomas  Follow

It is achiral. The cyclopropane ring is planar. The substituted C will be $\mathrm{sp^3}$ hybridised (tetrahedral). If you consider two of the C's in one plane and the H and Br in the other plane, these two planes will make 90° angle between them and one can draw a mirror plane along the plane containing H and Br. Thus, it will be achiral.

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Electricity & Electronics  Follow
Note: every 3-atom ring must be planar no matter what else is on it, because 3 points define a planeMore
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Fahim ul Haq  Follow
Nit-pick - 3 non co-linear points define a plane. That said I once lost marks during my degree in an organic chemistry piece of work for this very explantation of the planarity of the carbons in cyclo-propanes as the tutor didnt understand my comment.More
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