SCH4U Reactions of Hydrocarbons

General summary: note that the table shows most common reactions and not all reactions.

Reaction Type / Organic Molecule / Other Reagents and Conditions / Products
Combustion / ALL / oxygen / CO2, H2O, (NO2 if N is present)
Addition / alkenes / HX* or X2, (room T) / Haloalkane
alkenes / H20*, (H2SO4 catalyst) / alcohol
alkynes, alkynes / H2, (pressure, heat) / alkanes
Substitution / alkanes / X2, (heat or light) / Haloalkane+HX
aromatics / X2 (catalyst FeBr3) / halobenzene + HX
aromatics / alkyl halide, (catalyst AlCl3) / alkylbenzene + HX
aromatics / HNO3, (H2SO4 catalyst) / Nitrobenzene + H2O
alcohol / HX (catalyst, ZnCl2 a.k.a. Lucas reagent) / Haloalkane + H2O
haloalkane / NaOH / Alcohol + NaX
Elimination / haloalkane / NaOCH2CH3,( heat) / Alkene +ethanol+NaCl
alcohol / (H2SO4, 1000C) / Alkene + H2O

  * Markovnikov’s Rule: The H of HX and H2O attaches mostly at the end of the double bond with the most hydrogens.(Known as the Rich gets Richer)

Reaction Type / Organic Molecule / Other Reagents and Conditions / Products
Oxidation / 10 alcohol / [O], KMnO4, K2Cr2O7 / Aldehyde
20 alcohol / Ketone
Aldehyde / Carboxylic acid
Reduction / Ketone / Alcohol
Aldehyde / Alcohol

Preparing esters: Esterification reaction

•  Specific type of condensation because water is produced.

•  Reaction between a carboxylic acid and an alcohol.

•  Conditions: acid catalyst and heat are required

Reactions of esters: Hydrolysis

•  the ester bond is hydrolysed (split in two) to form two products.

•  produces the salt of a carboxylic acid and an alcohol.

•  Carried out in an acidic condition and usually requires heat

•  Saponification is an example of hydrolysis - soap is made by the basic hydrolysis of ester bonds in vegetable oils or animal fats

Preparing amides: condensation reactions

•  Description: reaction between an amine or ammonia and a carboxylic acid to produce an amide and water.

Reactions of amides: hydrolysis

•  Amides undergo hydrolysis reactions (like esters)

•  The hydrolysis of amides produces an amine and a carboxylic acid. This requires basic (NaOH) or acidic (H2SO4) conditions with some heat.

Synthetic Addition Polymers

Polymers

•  Polymer: very long molecule that is made by linking together many smaller molecules called monomers.

•  Compared to joining paper clips together in a long chain where each paper clip represents a monomer.

•  Polymers can be made of just one type of monomer, or a combination of two or more different monomers.

•  Example: -A-A-A-A-A-A-A-

-A-B-A-B-A-B-A-B-A-B

-A-A-B-A-B-B-B-A-B-A

-A-A-A-A-B-B-B-B-

•  Polymerization: process by which monomers are joined to form polymers

General Classes of Polymers

•  chain growth (addition) polymers (often by “radical polymerization”)

•  step growth (condensation) polymers

Addition Polymerization

•  Reaction in which monomers with double bonds are joined together through multiple addition reactions to form a polymer

•  Consists of three steps:

•  initiation

•  propagation

•  termination

•  Step 1: Generate a radical initiator

•  Step 2: Propagation – lengthens the chain

–  the electrons shift in the newly bonded molecule, leaving one unpaired electron at the other end of its original double bond

–  this unpaired electron forms another covalent bond with another atom or group.

•  Step 3: Termination – terminates the reaction when two unpaired electron ends combine forming a single covalent bond.

There are many types of addition polymers

polymer = polyethylene or polyethene (or ethylene)

Monomer / Polymer Name / Uses
H2C=CH2
H2C=CHCH3
H2C=CHCl
H2C=CH
H2C=CHCN
H2C=CCO2CH3
H2C=CHOCOCH3
H2C=CHOH
F2C=CF2

Properties of plastics

•  Plastics are polymers of substituted ethene (vinyl)

•  Chemically unreactive

•  Used for containers for chemicals, foods, etc

•  Intermolecular forces: van der Waals and some electrostatic attractions for substituted groups

•  Plastics are flexible and moldable due to weak intermolecular forces

Substituted Groups

Teflon

•  CF2=CF2

•  Strong C-F bonds account for unreactivity of teflon and its non-stick properties even at high temperatures

Plexiglass

•  One H on ethene is replaced by –COOCH3

•  Group responsible for transparency and optical properties

•  Presence of carbonyl group makes plexiglass soluble in other organic solvent containing a carbonyl group such as acetone

Crosslinking

•  Occurs when monomers have two double bonds

•  Dienes have two locations where addition can occur

•  Dienes can attach to two separate chains at the same time (bridge)

•  These bridges (crosslinks) hold the chains together making the polymer much stronger

•  Amount of diene added dictate the rigidity of the polymer

•  An example of a crosslinking agent is (1,4-diethenylbenzene)