Reactions Flashcards
(14 cards)
Addition reaction
Occur in alkenes.
the double C=C bond breaks, leaving a single C-C bond and 2 spare electrons which form 2 new bonds.
Two atoms or atom groups are added, 1 to each previously double bonded C atom.
There are 4 main types
Hydrogenation (H2/Pt or Pd or Ni)
Hydration (conc. H2SO4 and H2O)
Halogenation (Br2/Cl2/HBr/HCl)
Polymerisation (monomer to Polymer)
Hydrogenation
Hydrogenation (H2/Pt)
hydrogen is added across the broken double C=C bond.
this occurs on a Platinum (Pt), Palladium (Pd) or Nickel (Ni) Surface
Always forms an alkane
ALKENE → ALKANE
Hydration
Hydration (H+/H2O)
water is added across the broken double C=C bond as an H atom and an OH functional group.
This occurs in the presence of conc. Sulfuric acid which we just show as H+
Always forms an Alcohol
ALKENE → ALCOHOL
For major Product the single H atom bonds with the Richest so the one with the most H atoms
Halogenation
Halogenation (Br2 / Cl2)
A halogen is added across the broken double C=C bond.
Always forms a Haloalkane
ALKENE -> Haloalkane
Halogenation with HBr and HCl
Halogenation (HBr / HCl)
Markovnikov’s rule applies to addition reactions when both the alkene and the reagent are asymmetrical e.g. HBr & HCl
Major Product: the H atom will add to the double bonded C atom which already had more H atoms for the majority of molecules. this is the Major product.
Minor Product: the H atom will add to the double bonded C atom which already had fewer H atoms for the minority of molecules. this is the minor product.
THE RICH GET RICHER!
ALKENE -> Haloalkane
Polymerisation
The double bond in each propene unit is broken leaving a single c-c bond and enabling two new c-c bond to form between monomers therefore connecting many of the monomers into long repeating polymer chains
Elimination reactions
The functional group and a H atom from an adjacent C atom are removed and a C-C double bond forms between the 2 atoms that lost atoms/groups.
There are only 2 elimination reactions ;
1. Conc. H2SO4 dehydrates (removes water) from alcohols.
2. KOH in alcohol eliminates HCl or HBr from a haloalkane
Elimination reactions with saytevs rule
Saytsev’s Rule
• this rule applies to elimination reactions when the haloalkane or alcohol reagent is asymmetrical.
Major Product ; the double bond will form between the C atom which had the functional group and the adjacent C atom with fewer H atoms for the majority of molecules. • this is the major product.
Minor product ; the double bond will form between the C atom which had the functional group and the adjacent C atom with more H atoms for the minority of molecules. • this is the minor product.
Substitution reactions
The removal of one atom/group (usually the functional group) and replacing it with a different atom/group.
There are 4 different types:
- alcohol to haloalkane with PCl3,PCl5 or SOCl2 reagents
- alkane to haloalkane with Br2/Cl2 and UV light
- Haloalkane to amine with conc. NH3/ alcohol reagent
- haloalkane to alcohol with KOH(aq) reagent
Oxidation reactions -reagent names
KMnO4, potassium permanganate
K2Cr2O7, potassium Dichromate
Diol means 2 alcohol groups
Oxidation reactions - observations
KMnO4 potassium permanganate is purple to colourless
K2Cr2O7 potassium dichromate is orange to green
Oxidation reactions- adding oxygen
- → Oxygen is added (or the number of bonds between C & O increase.There are only 2 oxidation reactions:
- Primary alcohols are oxidised to carboxylic acids (by either KMnO4 / H+ or K2Cr2O7 / H+)
- Alkenes are oxidised to diols (2 alcohol groups) by KMnO4 only
Acid+base reactions
Acid + Base —> Salt +water
- all carboxylic acids are weak acids
Acid+base reactions
Acid + Base —> Salt +water
- all carboxylic acids are weak acids
