EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:4.4.1 Alkenes

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:4.4.1 Alkenes

The Alkenes

 

  • All alkenes contain a double carbon bond, which is shown as two lines between two of the carbon atoms i.e. C=C
  • All alkenes contain a double carbon bond, which is the functional group and is what allows alkenes to react in ways that alkanes cannot
  • The names and structure of the first four alkenes are shown below:

 

 

Table Showing the Formulae and Structures of the First Four Alkenes

7.2.1-Alkenes-First-5-members-1-17.2.1-Alkenes-First-5-members-1-2

 

 

  • Compounds that have a C=C double bond are also called unsaturated compounds
  • That means they can make more bonds with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group
  • Each of these carbon atoms now forms 4 single bonds instead of 1 double and 2 single bonds
  • This makes them much more reactive than alkanes

 

 

Double-Bond-Opening

 

A carbon-carbon double can break and form a single bond, allowing more atoms to attach to the carbon atoms

 

 

Exam Tip

The numbers in butene, pentene and hexene refer to the carbon atom in which the C=C begins, counting from the left. E.g. pent-2-ene, C5H10 has the C=C between the 2nd and 3rd carbon atoms. In pent-3-ene the C=C bond is between the 3rd and 4th carbon atoms from the left.

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