R3 will represent alkyl, substituted alkyl, aryl or substituted aryl and {HEAD ~ its formula} will be determined by the make up of R1 and {TAIL ~ R2} 
R3 will represent alkyl , substituted alkyl , aryl or substituted aryl and { HEAD ~ its formula } will be determined by the make up of R1 and { TAIL ~ R2 }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL