halogenalkanes

• Who is the presenter of the video on ecology no alkanes?

  Chris Harris
• What is the purpose of the video on ecology no alkanes?

  To provide an overview of the topic and content expected for the AQA exam
• Where can viewers purchase the PowerPoint used in the video?

  By clicking the link in the description box below the video
• What are halogen alkanes?

  Alkanes that have one or more halogens attached to them
• How do you name halogen alkanes?

  Find the longest carbon chain and use prefixes for the halogens in alphabetical order
• What is the product formed from the nucleophilic substitution of 1-bromopropane with KOH?

  1. propanol
• What is the nucleophile in the reaction of halogenalkanes with KOH?

  :OH-
• What is the overall equation for the reaction between 1-bromopropane and KOH?

  CH3CH2CH2Br + KOH → CH3CH2CH2OH + KBr
• What is the mechanism name for the reaction of halogenalkanes with nucleophiles?

  Nucleophilic substitution

  
• What is a radical in the context of free radical substitution?

  A species with an unpaired electron
• How do radicals behave?

  They are unstable, high energy, and highly reactive
• What type of bond breaking occurs during the initiation and propagation stages of free radical substitution?

  Homolytic fission
• What is the major disadvantage of free radical substitution?

  It forms a mixture of products as a random process
• What is the overall equation for the reaction between methane and chlorine?

  CH4 + Cl2 → CH3Cl + HCl
• What are the three stages of free radical substitution?

  1. Initiation: UV light causes Cl2 to dissociate into radicals.
  2. Propagation: Radicals react with alkanes to form new radicals.
  3. Termination: Radicals combine to form stable products.
• What is the initiation reaction for chlorine radicals?

  Cl2 → ●Cl + ●Cl
• What happens during the propagation stage of free radical substitution?

  Radicals react with other molecules to form new radicals
• What is the termination step in free radical substitution?

  ●Cl + ●CH3 → CH3Cl
• Why do halogenalkanes react with nucleophiles?

  Halogens are electronegative, causing a polar bond
• What are the three nucleophiles to recall in year 12?

  :OH-, :CN-, :NH3
• What is the equation for the natural formation and breakdown of ozone?

  O2 + ●O ⇌ O3
• Why is high energy radiation a problem on Earth?

  It causes skin cancer and eye problems
• What is a CFC?

  Chloro Fluoro Carbon
• What do CFCs form with high energy UV radiation?

  Chlorine radicals
• What is the initiation reaction for CF2ClCF3?

  CF2ClCF3 → ●CF2CF3 + ●Cl
• Why do the C-F bonds not break with UV light?

  They are too strong to break with UV light
• What are the two propagation equations involving chlorine radicals?

  ●Cl + O3 → O2 + ●ClO and ●ClO + O3 → 2O2 + ●Cl
• How do chlorine radicals behave in the ozone layer?

  As a catalyst: used in one step and regenerated
• What effect do small amounts of chlorine radicals have on the ozone layer?

  They keep decomposing the ozone layer
• What alternatives do we have for CFCs?

  HCFCs and HFCs
• Why are HCFCs and HFCs considered better alternatives to CFCs?

  They do not produce ●Cl
• What is the overall equation for the reaction between 1-bromopropane and KCN?

  CH3CH2CH2Br + KCN → CH3CH2CH2CN + KBr
• What is the nucleophile in the reaction of halogenalkanes with KCN?

  :CN-
• What is the overall equation for the reaction between 1-bromopropane and NH3?

  CH3CH2CH2Br + 2NH3 → CH3CH2CH2NH2 + NH4Br
• Why is excess ammonia needed in the reaction with halogenalkanes?

  To reduce further substitution as the amine can behave as a nucleophile

  
• How does the halogen affect the reactivity of halogenalkanes?

  Reactivity increases down the group as bond strength decreases
• What is elimination in the context of halogenalkanes?

  The loss of a small molecule
• What reagents are used in elimination reactions of halogenalkanes?

  NaOH
• How does OH- behave in elimination reactions?

  As a base
• Which hydrogen is attacked by the OH- base in elimination reactions?

  A hydrogen on the carbon next to the carbon-halogen