Write the structure formula of propane,propanol,butanol,pentane 2,1 pentane 3,1 and propanone

Here are the structural formulas for the requested compounds. For "pentane 2,1" and "pentane 3,1", these are not standard IUPAC names. I will assume you meant pentan-2-one and pentan-3-one, respectively, given the inclusion of propanone.

• Propane (an alkane): $\boxed{\text{CH}_3\text{CH}_2\text{CH}_3}$

• Propanol (assuming propan-1-ol, an alcohol): $\boxed{\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}}$

• Butanol (assuming butan-1-ol, an alcohol): $\boxed{\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH}}$

• Pentan-2-one (assuming "pentane 2,1" refers to this ketone): $\boxed{\text{CH}_3\text{C}(=\text{O})\text{CH}_2\text{CH}_2\text{CH}_3}$

• Pentan-3-one (assuming "pentane 3,1" refers to this ketone): $\boxed{\text{CH}_3\text{CH}_2\text{C}(=\text{O})\text{CH}_2\text{CH}_3}$

• Propanone (a ketone, also known as acetone): $\boxed{\text{CH}_3\text{C}(=\text{O})\text{CH}_3}$