Isothermal multitube reactors and processes incorporating the same

A process for producing a chlorinated and/or fluorinated propene and higher alkene having the formula CH2−c−gClcFg═CH1−d−hCldFh—CH3−e−fCleFf wherein c is 0-2, d is 0-1, e is 0-3, f is 0-3, and g is 0-2 while c+g≦2, d+h≦1, and e+f≦3, comprising feeding a stream of chlorinated and/or fluorinated alkanes and chlorinated and/or fluorinated alkenes to an isothermal multitube reactor comprising a plurality of reactor tubes situated within a shell wherein the reactor utilizes a feed mixture inlet temperature at least 20° C. lower than a desired reaction temperature and wherein at least a portion of at least one reactor tube is definable by a Reynolds number of at least about 2100.