Most simple structures are entered as you would write them. Notice that you do NOT have to capitalize elements - FX ChemStruct almost always takes care of that for you.
Alkanes
ch3ch2ch2ch3
ch3(ch2)4ch3
Alkenes
ch2ch2
Alkynes
chch
Aldehydes
ch3ch2coh
Carboxylic Acids
ch3cooh
Ketones
ch3coch3
Ethers
ch3och3
Amides
ch3conh2
Esters
ch3cooch3
