Out here in the stroma, a bunch of different enzymes use the carbon dioxide molecules and hydrogen ions made during the light dependent phase to assemble sugar fragments which are half of a glucose molecule (just 3 carbon atoms, instead of the 6 required to make a complete glucose molecule).
An alkane, by definition, only has single bonds. Even if your second diagram made sense (it doesn't for the reason above) it would not be an alkane at all because there is a double bond. Alkanes are a functional group. It's called alkil. As a functional group they have the generic formula R(CH2)nH.
Alkanes are hydrocarbons in which the carbon atoms are held together by single bonds. Their general formula is C n H 2n+2 for molecules which do not contain ring structures.lkanes are hydrocarbons in which the carbon atoms are held together by single bonds. Their general formula is C n H 2n+2 for molecules which do not contain ring structures.