Question

Draw all structural and geometric isomers of butene and name them.

Short answer

The three isomers of butene are: 1. 1-butene: CH_2=CHCH_2CH_3 2. cis-2-butene (Z-but-2-ene): CH_3CH=CHCH_3 (methyl groups on the same side) 3. trans-2-butene (E-but-2-ene): CH_3CH=CHCH_3 (methyl groups on opposite sides)

Step-by-step solution

Determine molecular formula of butene

Butene is an alkene with four carbon atoms and a double bond. So its molecular formula is C_4H_8.

Draw the structural isomers

To draw the structural isomers of butene, we need to rearrange the position of the double bond and check if we can create any new structures: 1. Double bond at the first carbon atom: CH_2=CHCH_2CH_3 2. Double bond at the second carbon atom: CH_3CH=CHCH_3 Now, let's name these structural isomers, using IUPAC nomenclature: 1. CH_2=CHCH_2CH_3: The double bond is located at C-1. Hence, the name for this compound will be 1-butene. 2. CH_3CH=CHCH_3: The double bond is located at C-2. Hence, the name for this compound will be 2-butene.

Draw the geometric isomers

Now we will focus on drawing the geometric isomers of the newly found structural isomers. 1-butene does not have any geometric isomers, as the two hydrogens on the first carbon make it impossible to distinguish between cis and trans forms. For the second structural isomer, 2-butene, we can have two geometric isomers: 1. The two methyl (CH_3) groups are on the same side of the double bond (cis form). We call it (Z)-but-2-ene or cis-2-butene. 2. The two methyl (CH_3) groups are on opposite sides of the double bond (trans form). We call it (E)-but-2-ene or trans-2-butene. Thus, butene has a total of three isomers: 1-butene, cis-2-butene (Z-but-2-ene), and trans-2-butene (E-but-2-ene).