The rate constant for the first order transformation of cyclopropane to propene is 5.40 x 10-2/hr. What is the half-life of this reaction? What fraction of the cyclopropane remains after 51.2 hours? What fraction remains after 18.0 hours? Question: The rate constant for the first order transformation of cyclopropane to propene is 5.40 x 10-2/hr. What is the half-life of this reaction? What fraction of the cyclopropane remains after 51.2 hours?