Although {HEAD ~ the above reaction} can also take place in a gas phase, water necessarily exists in {TAIL ~ an actual environment} as mentioned earlier 
Although { HEAD ~ the above reaction } can also take place in a gas phase , water necessarily exists in { TAIL ~ an actual environment } as mentioned earlier
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH