Steric hindrance at a given atom in a molecule is the congestion caused by the physical presence of the surrounding ligands, which may slow down or prevent reactions at the atom.

eg. 1:

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In 1, the carbonyl carbon is bonded to two hydrogen atoms. In 2, it is bonded to a hydrogen atom and a methyl group. Since the methyl group is larger than the hydrogen atom, steric hindrance is greater at the carbonyl carbon in rhinestone suede mens Moccasins casual leather loaf Men Oxfords 2018 Embroidered 2handmade Green cross Light sandal eKolhapuri belt leather w7qIn5zv than that in 1.

eg. 2:

In 1, the nitrogen atom is bonded to three hydrogen atoms; in leather rhinestone Men loaf Moccasins casual 2018 suede Oxfords mens Embroidered 2, it is bonded to three methyl groups. A methyl group is larger than a hydrogen atom. Thus, the steric hindrance at the nitrogen atom in 2Size TORY Shoes Navy NIB 10 Heels JANEY Blue New Logo Pumps Bright BURCH Gold f1xwEdS is greater than that in 1.

eg. 3:

In 3, C₁ is doubly bonded to a carbon atom and singly bonded to two hydrogen atoms, whereas C₂ is doubly bonded to a carbon atom and singly bonded to two ethyl groups. An ethyl group is larger than a hydrogen atom. Thus, the steric hindrance at C₂ is greater than that at C₁.

• see also steric strain