CIE A Level Biology复习笔记2.2.2 Covalent Bonds in Polymers

Covalent Bonds in Polymers

  • A covalent bond is the sharing of two or more electrons between two atoms
    • The electrons can be shared equally forming a nonpolar covalent bond or unequally (where an atom can be more electronegative δ-) to form a polar covalent bond
  • Generally each atom will form a certain number of covalent bonds due to the number of free electrons in the outer orbital e.g. H = 1 bond, C = 4 bonds
  • Covalent bonds are very stable as high energies are required to break the bonds
  • Multiple pairs of electrons can be shared forming double bonds (e.g. unsaturated fats C=C) or triple bonds

6-Covalent-bonds

Different types of covalent bonds

  • When two monomers are close enough that their outer orbitals overlap this results in their electrons being shared and a covalent bond forming. If more monomers are added then polymerisation occurs (and / or a macromolecule forms)

Condensation

  • Also known as dehydration synthesis (‘to put together while losing water’)
  • A condensation reaction occurs when monomers combine together by covalent bonds to form polymers (polymerisation) or macromolecules (lipids) and water is removed

6-Condensation-reaction

Written and symbolic illustrations of the removal of water to form a covalent bond between two or more monomers during a condensation reaction

Hydrolysis

  • Hydrolysis means ‘lyse’ (to break) and ‘hydro’ (with water)
  • In the hydrolysis of polymers, covalent bonds are broken when water is added

6-Hydrolysis-reaction

Written and symbolic illustrations of the addition of water to break down covalent bond/s during a hydrolysis reaction

Covalent bonds in organic molecules table

Covalent-bonds-in-organic-molecules-table

Exam Tip

You must be able to recognise and identify the location of the covalent bonds in the molecules – note that these molecules may be unfamiliar to you.

 

 

 

 

 

 

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