haloalkanes Flashcards
free radical substitution
UV light- provides energy required to break the halogen-halogen bond at the start of the reaction
Definition: A species with an unpaired electron
mechanism:
Initiation- Cl2–> 2Cl*
Propagation- Cl* + CH4 –> CH3 + HCl
CH3 + Cl2 –> CH3Cl + Cl
termination:
CH3 + *Cl –> CH3Cl
2CL –> Cl2
2CH3 –> CH3CH3
(two radicals combine)
Curly arrow use
To shpw the movement of electrons
Nucleophile definition
An electron-pair donor
Strength of C=C bond
C=C bond is stronger than a single bond because it has more electrons. A pie bond is weaker than a sigma bond. A pie bond is more reactive. Allene is more reactive. Can’t react because the pie bond is formed by an overlap of p orbitals and this would be lost resulting in a break of bond.
Definition of an electrophiles
Accepts a electron pair
Major and minor products
X is made from a 2º carbocation whereas Y is made from a 1º carbocation. 2º is more stable due to a more positive inductive effect.
Why does bromine react in electro Philip addition even though its a non-polar molecule
C=c is electron rich, this induces a dipole across the Br2 molecule. The d+ Br atom accepts an electron pair.
Test for Alkenes
Bromine water
Allene= orange to colourless
Anything else-nvc
CH2=CH2 +Br2 —> CH2BrCH2Br
Aldehyde
Structural formula: CHO
Ending: al
Carbonyl bonded to at least 1H atom
Ketone
Carbonyl bonded to 2 carbon atoms
Structural formula: CO
Ending: one
Carboxylic acid
Carbonyl bonded to an OH group
Ending: oic acid
Structural: COOH
Oxidation of alcohols
Acidified K2Cr2H7 and conc sulfuric acid
Turns orange to green
Reagent. O used H20 produced. Product. Conditions
Primary alcohol. 1. 1. Aldehyde Distillation
Aldehyde. 1. 0. Carboxylic acid Reflux
Primary alcohol 2. 1. Carboxylic acid. Reflux
Secondary alcohol. 1. 1. Ketone. Reflux or distillation
Oxidation statements
Features of condenser: open at both ends, cold water flows around outside
Purpose of condenser: cool hot vapour condenses it to a liquid
Anti bumping granules used to prevent formation of larger bubbles
Test for aldehyde
Tollens: forms silver mirror
Equation: [Ag(NH3)2]+ +e- —> Ag (s) +2NH3
Fehling’s: forms brick red precipitate
Equation: Cu2+ +e- —> Cu+
Test for Carboxylic acid
Na2CO3- forms effervescence
Equation: CO32- +2H+ —> CO2 + H20
Primary alcohol –> aldehyde
K2Cr2O7, acidified with conc H2SO4, heat under distillation
CH3CH2OH + [O]–> CH3CHO + H2O
Aldehyde –> Carboxylic acid
K2Cr2O7, acidified with conc H2SO4, heat under reflux
CH3CHO + [O]–> CH3COOH
1º alcohol –> carboxyllic acid
K2Cr2O7, acidified and heat under reflux
CH3CH2OH + 2[O] –> CH3COOH + H20
2º –> ketones
K2Cr2O7. acidified , heat under reflux or distillation
CH3CH9OH)CH3 + [O] –> CH3COCH3 + H2O
3º cant react because no hydrogens aren’t available on the carbon.
Why is reflux used to oxidise a 1º alcohol to carboxyllic acid
To prevent any vapour escaping from the reaction mixture.
hat happens to the aldehyde as it is produced during distillation
Aldehyde boils and vaporises, then escapes from the mixture.
Ethanol can be oxidies to ethanal or ethanoic acid. describe how ethanal can be made in high yield, as opposed to ethanoic acid
heat mixture to boiling point of ethanal, set up distillation. maintain temp at boiling point so aldehyde is condensedto a liquid and collected.
Why no rotation around double bond
The pie bond is formed by overla of p orbitals. if any rotation, p orbiyals would no longer overlap and pie bond would break.
What is a positive inductive effect
The ability to release electron density through a covalent bond
