Organic Reactions Summary PDF

Organic chemical Reactions Reduction Reactions AElectronegativity d d i t i o n –R e a c t i o n s There are 2 main types: a) Ionic addition of Br₂, Cl₂, or HCl across C=C in ethene Require: a) Heat b) Polymerisation; ie. the joining together of small molecules to form larger molecules Substitution...

Organic chemical Reactions Reduction Reactions AElectronegativity d d i t i o n –R e a c t i o n s There are 2 main types: a) Ionic addition of Br₂, Cl₂, or HCl across C=C in ethene Require: a) Heat b) Polymerisation; ie. the joining together of small molecules to form larger molecules Substitution Reactions There are 2 main types: b) A Ni catalyst c) Acid Reactions as acids a) Reactions of alcohol with sodium b) Reaction of carboxylic acids a) Halogenation of methane & ethane with: (ie. Subbing Br, Cl, etc. for a H) b) Esterification (reaction between carboxylic acids & alcohols) elimination reactions Removal of a small molecule from a large molecule, leaving a C=C behind. 4. Redox Reactions: Use of an oxidising agent : Potassium Permanganate, Sodium Dichromate a) Primary alcohol → Carboxylic acid Secondary alcohol → ketone b) Aldehyde c) → aldehyde i. Magnesium ii. Sodium Hydroxide iii. Sodium Carbonate polymerisation Organic chemical Reactions Esterification is a substitution reaction between This happens for 2 reasons: a carboxylic acid & an alcohol to form an 1. Inductive Effect The carbon is δ⁺ ester. It tends to attract the electron from O. hydrolysis is the chemical decomposition of a substance This further polarises the O-H bond and allows for the removal of the H 2. Stability of the ethanoate ion by water, with water itself also being decomposed. 1. Primary alcohols: This is where the carbon attached to the OH group is attached to only one other carbon. 2. Secondary alcohols: Reaction Mechanism for Halogenation of Alkenes This is where the carbon attached to the IONIC ADDITION OF BROMINE TO OH group is attached to 2 other carbons. ETHENE Example: Propan – 2 – ol Note: The same mechanism is used for ethene + Cl2 or HCl) Step 1: end on approach of Br2 ACIDIC NATURE OF CARBOXYLIC ACIDS: When ethanoic acid reacts, it loses this hydrogen: The double bond contains 4 electrons (ie. 2 bond pairs) & is a centre of negative charge. This polarises Br2 into Organic chemical Reactions Step 2: Polarisation becomes too Free Radical Substitution great & Br2 is split into Br+ & Step 1: Initiation: Br- (this bromine now has 2 U.V. light is used to split Cl₂ (Cl molecule) electrons from the bond pair) into 2 Cl atoms, each containing 1 electron from the double bond. Each Cl is known as a free radical & they are very reactive due to the This step is known as presence of the unpaired electron. heterolytic fission Step 2: Propagation: Step 3: Br⁺ attacks the C=C in an effort to gain its lost electron. Br⁺ gains the electron by forming a covalent bond with A Cl free radical attacks a methane molecule to form HCl & a methyl radical The methyl free radical (CH₃ ) is unstable & wants to react immediately one of the double bonded C’s; in the process it breaks the C=C. It attacks a Cl₂ molecule forming chloromethane (the desired haloalkane) & a Cl radical. This is an example of a chain reaction This leaves the other carbon It involves CH₄ reacting with without an electron; ie. It is now Cl to produce CH₃ C⁺ This CH₃ in turn reacts with Cl2 C⁺ is an extremely unstable ion called a carbonium ion. to produce Cl This Cl radical will attack a Step 4: CH₄, restarting the process. The carbonium ion (C⁺) is now attacked by the Br⁻ ion resulting in the formation of 1,2 – dibromoethane. Organic chemical Reactions Step 3: Termination begins to occur when the concentration of chlorine molecules drops (ie. no new Cl being formed). Termination involves various free radicals coming together to form unreactive molecules: