Halogenoalkenes
- Created by: elliee02
- Created on: 23-03-19 15:12
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- HALOGENO ALKANES
- NAMING
- Bromo- (Br)
- Chloro- (Cl)
- Iodo- (I)
- Primary - halogen attached to carbon which is attached to 2 H and 1 Alkyl group
- Secondary - halogen attached to Carbon which is attched to 1 H and 2 Alkyl groups
- Tertiary - Halogen attached to Carbon whicb is attached to 3 Alkyl groups
- INVESTIGATING RATE OF HYDROLYSIS
- OF CHLORO, BROMO AND IODO
- Conditions; warm with aq silver nitrate solution in ethanol
- Iodoalkane forms quickest then bromoalkane then chloroalkane
- C-I bond is weakest so requires less energy to break bond so rate of reaction is quickest
- C-Cl bond is strongest and so requires more energy to break bond so rate of reaction is slowest
- Rate is not determined by size of dipole as otherwise the trend would be opposite to the one observed
- Ethanol is used as a co-solvent to mix the AgNO3 and X-alkane mix
- Draw a cross on the back of 3 test tubes. Add HALOALK into test tube with silver nitrate and ethanol. Put in test tube stand. Start stopwatch. Time how long it takes for cross to disapear
- Fair test
- Same vol of all substances
- use same water bath at same time to keep temp constant
- OF PRIMARY, SECONDARY AND TERTIARY
- E.g 1-bromobutane, 2-bromobutane and 2-bromo-2methylbutane
- Tertiary fastest then secondary then primary slowest
- Tertiary react via SN1 (substitution nucleophilic bimolecular) reaction pathway, which is a quicker mechanism
- Tertiary can't react via SN2 as the steric hindrance of the Alkyl groups prevent the nucleophile from attacking the central Carbon s+
- Primary HALOALK cannot react via SN1 because the primary carbocations are not stable enough to form in the first step
- Secondary HALOALK react via via an intermediate mechanism - draw either SN1 or SN2
- Tertiary react via SN1 (substitution nucleophilic bimolecular) reaction pathway, which is a quicker mechanism
- React each HALOALK with silver nitrate solution in the presence of ethanol in a water bath. Record time fore precipitate to obscure a cross
- OF CHLORO, BROMO AND IODO
- Nucleophile - species which attacks a region of S+ by donating a lone pair of electrons to form a dative covalent bond
- Reaction with Aq silver nitrate in ethanol
- water acts as nucleophile
- Warm with aq ailver nitrate and ethanol
- alcohol formed, H+ ion and halide ion then silverhalogen formed
- Nucleophilic substitution
- substitution
- Reaction with potassium cyanide, KCN
- Heat with potassium cyanide
- Lengthens Carbon chain
- Substitution
- Nucleophilic substitution
- Nucleophile is c=N (triple bond)
- Nitrile formed
- Reaction with Ammonia, NH3
- Heat with ammonia solution
- Substitution
- Nucleophilic substitution
- Amine formed
- Reaction with Aq potassium hydroxide, KOH
- Alcohol and ion formed
- Nuclophilic substitution
- Substitution
- Heat under reflux with aq potassium hydroxide solution
- Reaction with potassium hydroxide in ethanol
- Heat with KOH dissolved in ethanol
- Eliminatin
- Alkene formed
- Alkene, hydride ion and water formed
- In exam, draw either SN1 or SN2
- NAMING
- Reaction with Aq potassium hydroxide, KOH
- Alcohol and ion formed
- Nuclophilic substitution
- Substitution
- Heat under reflux with aq potassium hydroxide solution
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