State that the bonding in alkenes includes a double carbon-carbon covalent bond and that alkenes are unsaturated hydrocarbons

What are Alkenes?

Alkenes are unsaturated hydrocarbons that contain at least one double bond between two carbon atoms. The general formula is C_nH_2n.

Think of a double bond like a handshake between two friends: they share two pairs of electrons, making the connection stronger and more reactive. In chemistry, this is written as \$C=C\$ (⚛️).

Because they have fewer hydrogen atoms than alkanes, alkenes are called unsaturated – they can “take in” more atoms (like hydrogen or halogens) during reactions.

Exam Tip: Remember the Formula!

When you see a compound with a double bond, quickly check if its formula matches C_nH_2n. If it does, it’s almost certainly an alkene. This is a quick way to spot the answer in multiple‑choice questions. 📚

Common Alkenes & Their Uses

Reaction Highlight: Hydrogenation

Alkenes can be “saturated” by adding hydrogen atoms across the double bond. This is called hydrogenation:

\$C=C + H_2 \rightarrow C-C\$

Imagine the double bond as a tight pair of friends; hydrogenation is like inviting a third friend to join, making the group (molecule) more stable. This reaction is used to produce liquid fuels from vegetable oils. 🚗

Quick Check: Is This an Alkene?

1. Does the molecule contain a double bond between two carbon atoms? 🔍
2. Does the formula fit C_nH_2n (e.g., C₄H₈)? ??

3. Are there any other heteroatoms (O, N, etc.) attached to the double bond? If yes, it might be an alkene derivative (like an alkene oxide). ❓

Answering these three questions quickly will help you identify alkenes in exam questions. Good luck! 🎓