{ diff(x1, t) = (-1)*k2*k3*x2*x1/k2,
  diff(x2, t) = (-1)*k2*k3*x2*x1/k2,
  diff(x3, t) = (1*k2*k3*x2*x1 + (-1)*k2*k7*x3*x4 + 1*k2*k8*x9)/k2,
  diff(x4, t) = (1*k2*k4*x5^2 + (-1)*k2*k5*x4 + (-1)*k2*k7*x3*x4 + 1*k2*k8*x9 + 1*k2*k12*x11)/k2,
  diff(x5, t) = ((-2)*k2*k4*x5^2 + 2*k2*k5*x4)/k2,
  diff(x6, t) = ((-1)*k2*k6*x6*x8 + 1*k2*k11*x10)/k2,
  diff(x7, t) = (1*k2*k6*x6*x8 + (-1)*k2*k9*x7*x9 + 1*k2*k10*x10)/k2,
  diff(x8, t) = ((-1)*k2*k6*x6*x8 + (-1)*k2*k13*x8*x18 + 1*k2*k25*x12 + 2*k2*k26*x19 + 3*k2*k27*x22)/k2,
  diff(x9, t) = (1*k2*k7*x3*x4 + (-1)*k2*k8*x9 + (-1)*k2*k9*x7*x9 + 1*k2*k10*x10)/k2,
  diff(x10, t) = (1*k2*k9*x7*x9 + (-1)*k2*k10*x10 + (-1)*k2*k11*x10)/k2,
  diff(x11, t) = (1*k2*k11*x10 + (-1)*k2*k12*x11)/k2,
  diff(x12, t) = (1*k2*k12*x11 + (-1)*k2*k14*x12*x13 + 1*k2*k15*x14 + (-1)*k2*k25*x12)/k2,
  diff(x13, t) = ((-1)*k2*k14*x12*x13 + 1*k2*k15*x14 + 1*k2*k19*x17 + (-1)*k2*k20*x13*x19 + 1*k2*k24*x21)/k2,
  diff(x14, t) = (1*k2*k14*x12*x13 + (-1)*k2*k15*x14 + (-1)*k2*k16*x14*x15 + 1*k2*k17*x16)/k2,
  diff(x15, t) = (1*k2*k13*x8*x18 + (-1)*k2*k16*x14*x15 + 1*k2*k17*x16 + (-1)*k2*k21*x15*x17 + 1*k2*k22*x20)/k2,
  diff(x16, t) = (1*k2*k16*x14*x15 + (-1)*k2*k17*x16 + (-1)*k2*k18*x16)/k2,
  diff(x17, t) = (1*k2*k18*x16 + (-1)*k2*k19*x17 + 1*k2*k20*x13*x19 + (-1)*k2*k21*x15*x17 + 1*k2*k22*x20)/k2,
  diff(x18, t) = ((-1)*k2*k13*x8*x18 + 1*k2*k18*x16 + 1*k2*k23*x20)/k2,
  diff(x19, t) = (1*k2*k19*x17 + (-1)*k2*k20*x13*x19 + (-1)*k2*k26*x19)/k2,
  diff(x20, t) = (1*k2*k21*x15*x17 + (-1)*k2*k22*x20 + (-1)*k2*k23*x20)/k2,
  diff(x21, t) = (1*k2*k23*x20 + (-1)*k2*k24*x21)/k2,
  diff(x22, t) = (1*k2*k24*x21 + (-1)*k2*k27*x22)/k2,
  diff(x23, t) = (1*k2*k25*x12 + 1*k2*k26*x19 + 1*k2*k27*x22)/k2 }