Final answer:
The s-trans conformation of 1,3-butadiene is more stable than the s-cis conformation because it experiences less steric hindrance between the substituents adjacent to the double bonds.
Step-by-step explanation:
The question pertains to the stability of conformations of 1,3-butadiene, which can adopt either the s-cis or s-trans conformation. The s-cis conformation has the hydrogen atoms adjacent to the double bonds on the same side, while in the s-trans conformation, they are on opposite sides. The s-trans conformation of 1,3-butadiene is more stable compared to the s-cis conformation. This is because the s-trans conformation experiences less steric hindrance between the hydrogen atoms which are further away from each other. In contrast, the s-cis conformation forces the hydrogens into closer proximity, leading to greater steric strain. This concept is parallel to the behaviors seen in butane and alkenes where the most stable conformations minimize steric repulsion, such as the anti conformation in butane and the trans configuration in 2-butene.
In the context of butane, as an example provided, we understand that anti-staggered conformations are the most stable due to the optimal distance between bulky groups. Similarly, for 1,3-butadiene, relief from steric strain is a driving factor for increased stability in the s-trans conformation compared to the s-cis conformation which has increased steric interactions due to proximity of substituents.