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Flashcards in Alkenes (T3) Deck (12)
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1
Q

What are alkenes?

A
  • unsaturated hydrocarbons - they contain a carbon-carbon double bond - the presence of the double bonds means that they do not contain as many hydrogen atoms as the corresponding alkane
2
Q

What are the three smallest alkenes and their chemical formulas?

A
  • ethene: C2 H4 - propene: C3 H6 - butene: C4 H8
3
Q

How are the physical properties of alkenes similar to alkanes?

A
  • the small alkenes with up to four carbon atoms are gases - they are gases up to C4 H8
4
Q

How are the chemical reactions of alkenes similar to alkanes?

A

They also burn in air or oxygen to give carbon dioxide and water

5
Q

Explain what happens when bromine is added to an alkene

A
  • when bromine is added to an alkene, the alkene undergo an addition reaction - part of the double bond breaks, freeing up two electrons for additional hydrogen atoms and adding bromine atoms in the place of one of the hydrogens - bromine adds to alkenes without any need for heat or a catalyst - this reaction is often carried out using bromine solution
6
Q

What is produced if bromine is added to ethene?

A
  • 1,2-dibromoethane is produced - it is a colourless liquid
7
Q

Why is there no alkene with just one carbon atom?

A

Because all alkenes contains a carbon-carbon double bond

8
Q

Why would not every carbon in a alkene be linked by a double bond to the next one?

A
  • all it take is one double bond to be present to be an ‘-ene’ - an ‘-ane’ will always be single bonds
9
Q

What is CH2=CH2 and why would it be written like that?

A
  • ethene - its standard written formula is C2 H4 but by writing it as CH2=CH2 it highlights the double bond between the two carbon atoms
10
Q

Describe how propene only has one double bond…

A
  • C3 H6 - there is only one double bond in the structure - the end carbon with the single bond has three hydrogen atoms bonded to it - if each carbon atom was double bonded to the hydrogen atoms next to it there would be no spare electrons to bind to hydrogen atoms
11
Q

Describe how butene only has one carbon-carbon double bond…

A
  • C4 H8 - the end carbon has three hydrogen atoms bonded to it while the middle carbon only has one, balancing out the general formula
12
Q
A