Rate coefficients for the reactions C2H with C2H4, C2H6, and H-2 are measured over the temperature range 150-359 K using transient infrared laser absorption spectroscopy. The ethynyl radical is formed by photolysis of C2H2 with a pulsed excimer laser at 193 nm, and its transient absorption is monitored with a color center laser on the Q(11)(9) line of the A(2) Pi-X(2) Sigma transition at 3593.68 cm(-1). Over the experimental temperature range 150-359 K the rate constants of C2H with C2H4, C2H6, and H-2 can be fit to the Arrhenius expressions k(C2H4) = (7.8 +/- 0.6) x 10(-11) exp[(134 +/- 44)/T], k(C2H6) = (3.5 +/- 0.3) x 10(-11) exp[(2.9 +/- 16)/T], and k(H2) (1.2 +/- 0.3) x 10(-11) exp[(-998 +/- 57)]/T cm(3) molecule(-1) s(-1), respectively. The data for C2H with C2H4 and C2H6 indicate a negligible activation energy to product formation shown by the mild negative temperature dependence of both reactions. When the H-2 data are plotted together with the most recent high-temperature results from 295 to 854 K, a slight curvature is observed. The H-2 data can be fit to the non-Arrhenius form k(H2) = 9.2 x 10(-18)T(2.17+/-0.50)exp[(-478 +/- 165)/T] cm(3) molecules(-1) s(-1). The curvature in the Arrhenius plot is discussed in terms of both quantum mechanical tunneling of the 11 atom from H-2 to the C2H radical and bending mode contributions to the partition function.