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Alkenes
The properties and the reactions of Alkenes.
| Question | Answer |
|---|---|
| What are Alkenes: | Unsaturated Hydrocarbons, which means they contain a C=C, double bond. |
| What type of bonding is present in a Double Bond? | Sigma and Pi bonding, the Pi bonding makes it impossible for the |
| What shape does the C=C bond make the Alkene? | Planar. Flat! |
| What type of Stereoisomerism is shown in Alkenes? | E-Z Stereoisomerism, E meaning Opposite, where the high priority function groups are on the opposite sides and 'Z' meaning the same, when the high priority FG are on the same side. |
| How can you decide if it is Z or E stereoisomerism? | The high priority function groups are the ones that have a Higher Atomic mass directly attached to the Carbons in the double bond. |
| Why does EZ stereoisomerism come about? | The Carbon=Carbon double bond is unable to rotate around like the Alkanes with single bonds as there is a Pi bond in a double bond, this prevents rotation. |
| What type of reagents will react most readily with Alkenes? | Electrophiles. |
| Define Electrophile: | An electron pair acceptor. |
| Why are electrophiles attracted to the Carbon Carbon double bond? | Because there are 4 electrons involved in a double bond and this is highly electron rich, making it very attractive to electrophiles. |
| What type of reactions will Alkenes under go usually? | Electrophilic Addition (addition of an Electrophile). |
| Why products can be made with the addition of water to an Alkene? What is the Catalyst for this reaction? | Alcohols and the catalyst is an Acid (The reaction is Acid-Hydrolysis). |
| Name 3 Reagents Usually reacted with Alkenes in an Electrophilic Addition reaction? | HBr (Hydrogen Halide), Br2 (Or a Halogen) and H2SO4 (Hydrosulfric Acid). The last one is a catalyst in making an Alcohol with Addition of water. |
| How can you test a substance for an Alkene (Unsaturation)? | Use Bromine liquid, it will turn brown to colourless. |
| What is the intermetiate stage of an Electrophilic addition reaction: | A Carbocation (A Hydrocarbon with a Positive charge). It is the likely stability of this compound which determines the location of the functional group. |
| Which Carbocations are the most stable, thus most likely? | Tertiary Carbocations (formed from Tertiary Alkenes). |
| Why are tertiary Carbocations more stable? | They are able to share the positive charge across many other carbon-carbon bonds, decreasing the overall effect the charge has. |
| What are polymers? | Long chain hydrocarbons formed from monomers, which have one unit repeating over. |
| How are polymers formed? | From Alkenes which undergo an Addition Polymerisation reaction. |
| Give two Polymers: | Polyethene (Polythene) which is used in Carrier Bags, Milk Crates, etc. Polypropane, which is used in Rope |
| Why are polymers useful? | They are usually used to form plastics, which are strong, unreactive and cheap to make. |
| What is one of the problems with using plastics from Alkenes? | They are not reactive, which means they are not biodegradable so natural enzymes cannot break them down (or take an age to do so!) Meaning they will fill up landfills etc. |
| What is one solution to making plastics more sustainable? | Recycling them, Mechanical recycling and Feedstock recycling. |
| Mechanical Recycling: | Melting down and remoulding large groups of a single type of plastic to repurpose it. Without breaking chains. |
| Feedstock Recycling: | The polymeres are heated to such a temp that the bonds break reforming the monomers allowing it to be reused as something else. |
Created by:
mjwilson1988
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