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| Frage | Antworten |
| What is a haloalkane? | An alkane with at least one halogen in place of a hydrogen atom |
| Complete the sentences: Halogens are generally much more _______________ than carbon, so the carbon-halogen bond is _________. The δ+ carbon is ___________-deficient. This means it can be attacked by a ________________ (an electron-pair donor) | Halogens are generally much more ELECTRONEGATIVE than carbon, so the carbon-halogen bond is POLAR. The δ+ carbon is ELECTRON-deficient. This means it can be attacked by a NUCLEOPHILE (an electron-pair donor) |
| Give 3 examples of nucleophiles | CN⁻ NH₃ OH⁻ |
| Haloalkanes can react with nucleophiles. What is the name of this reaction? | Nucleophilic substitution reaction |
| What happens in a nucleophilic substitution reaction? | A nucleophile attacks a polar molecule and replaces a functional group |
| Give the general symbol equation for nucleophilic substitution | RX + Nu⁻ --> RNu + X⁻ |
| Draw the mechanism for nucleophilic substitution reaction between C₂H₅X and a nucleophile |
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| What happens in hydrolysis reactions? | Molecules are split up by water molecules |
| Haloalkanes can be hydrolysed to make... | Alcohols |
| What are two ways in which haloalkanes can be hydrolysed to produce alcohols? | Hydrolysis with aqueous alkali Hydrolysis with water |
| Describe the method of hydrolysing haloalkanes with aqueous alkali, including the reactants and the type of reaction | Haloalkanes are hydrolysed by warm aqueous alkali, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution, in a nucleophilic substitution reaction |
| Give a general equation for the hydrolysis of haloalkanes with aqueous alkali | RX + ⁻OH --> ROH + X⁻ |
| TRUE OR FALSE: Hydrolysis with water is a slower reaction than the one with warm aqueous alkali | TRUE |
| Why is hydrolysis with water slower than with warm aqueous alkali? | The water molecule is a weak nucleophile, but it will eventually substitute for the halogen |
| Give a general equation for the hydrolysis of haloalkanes with water | RX + H₂O --> ROH + H⁺ + X⁻ |
| Complete the sentences: How quickly different haloalkanes are hydrolysed depends on ________ __________, Weaker carbon-halogen bonds break more easily - so they react _________. ________________ have the weakest bonds so they hydrolyse the fastest. _______________ have the strongest bonds, so they're the slowest. | How quickly different haloalkanes are hydrolysed depends on BOND ENTHALPY. Weaker carbon-halogen bonds break more easily - so they react FASTER. IODOALKANES have the weakest bonds so they hydrolyse the fastest. FLUOROALKANES have the strongest bonds, so they're the slowest. |
| Describe a method to compare the reactivities of different haloalkanes. | Haloalkanes can be hydrolysed with water to form alcohols. if you put silver nitrate solution in the mixture, the silver ions will react with the halide ions as soon as they form, giving a silver precipitate. You can use this reaction to compare reactivities. The rate of reaction could be measured using the 'disappearing cross' experiment. |
| Describe a method used to identify unknown haloalkanes |
React a sample of the haloalkane in a test tube with water in the presence of silver nitrate solution and ethanol.
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