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Alkenes

16/07/2014. Alkenes. L.O. I can draw the structural and molecular formula of the first four alkenes. I know the test for alkenes and can use it to identify an alkene from an alkane. C. C. Single covalent bond. C. C. Double covalent bond. Alkenes.

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Alkenes

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  1. 16/07/2014 Alkenes L.O. • I can draw the structural and molecular formula of the first four alkenes. • I know the test for alkenes and can use it to identify an alkene from an alkane.

  2. C C Single covalent bond C C Double covalent bond Alkenes • When carbon forms compounds each carbon atom always forms four bonds. • This does not, however, mean that each carbon is joined to four other atoms. • It is possible to have bonds grouped into pairs. These are called double bonds. • Alkenes contain carbon atoms joined by double covalent bonds.

  3. H H C C H H or Ethene - formula • The simplest alkene is ethene. • It has the formula C2H4 • The carbon atoms are joined together by a double bond. • Its displayed formula may be drawn in slightly different forms but should always clearly show the double bond.

  4. 16/07/2014 Alkenes Molecular formula Displayed formula Ethene C2H4 HH C C HH Propene C3H6 HH H C C C H HH

  5. 16/07/2014 Alkenes Molecular formula Displayed formula Butene C4H8 HH H H C C C C H HH H Pentene C5H10 HH H H H C C C C C H HH HH What is the general formula for the alkenes? – CnH????

  6. The general formula of the alkenes is CnH2n

  7. Activity H H H C H C C H H H H H H C H H C H H C H C H H H C C C H H C C H H H H • Sometimes the displayed formula is drawn as shown.

  8. Activity • What will be the formula for alkenes containing the following numbers of carbons? C11H22 C13H26 C32H64 C21H42

  9. Saturated or Unsaturated? • Alkanes are saturated. • Saturated means “full up”. • Every carbon atom has already used all four of it’s bonds to join to four other atoms. No other atoms can be added. • Alkenes are unsaturated. • They have a double bond that could instead become two single bonds. This means that other atoms can be added. It is not “full up”.

  10. Br2 + Gas red colourless Bromine water +alkene Test for Alkenes When bromine water is added to an alkane nothing happens but when bromine is added to an alkene the red colour of the bromine disappears. 1,2 dibromoethane

  11. Activity • Complete the blanks alkene C5H10 alkane C8H18 alkene C4H8 alkane C10H22

  12. Which of these is an alkene? • C6H14 • C4H8 • C12H26 • C102H206

  13. The formula of the alkene with 15 carbons is? • C15H30 • C15H60 • C15H32 • C15H28

  14. Hydrocarbons contain only which two elements? • Carbon and electron • Carbon and water • Carbon and oxygen • Carbon and hydrogen

  15. The bonds in a hydrocarbon are what type? • Covalent • Ionic • Complex • Metallic

  16. Which is the simplest Alkene? • Methene • Decene • Ethene • Butene

  17. Which is alkene has 5 carbons? • Propene • Pentene • Pectane • Proptene

  18. What is the molecular formula of Butene? • C3H6 • C4H8 • C2H4 • C6H12

  19. What do alkanes do to Bromine water? • Produce layers • Turn it colourless • Leave it unchanged

  20. Bingo 1. Alkanes 9. Bromine water 2. Methane 10. covalent 3. C2H6 11. propane 4. Carbon 12. colourless 5. Hydrogen 13. electron 6. Orange 14. C2H4 7. ethene 15. alkene 8. Six 16. butene

  21. Homework Complete sheet on the alkenes.

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