Celsius to Kelvin conversion formula
The temperature T in Kelvin (K) is equal to the temperature T in degrees Celsius (°C) plus 273.15:
T(K) = T(°C) + 273.15
So to convert the boiling point of cyclopropane from degrees Celsius to kelvin:
T(K) = T(°C) + 273.15
T(K) = -33 + 273.15
T(K) = 240.15 K