Chemical structure at the turnoff of the 4.0 M_⊙ star computed without rotation and with rotation for an initial rotation velocity of 300 km s^-1 (top and bottom panels respectively). The mass fractions are multiplied by 600 for ³He, by 100 for ¹²C and ¹⁴N, by 2500 for ¹³C, by 50, 5000, and 6 × 10⁴ for ¹⁶O, ¹⁷O, and ¹⁸O respectively, and by 1500 for ²³Na. The vertical arrows show, in both cases, the maximum depth reached by the convective envelope at its maximum extent during the first dredge-up.