Organic Chemistry Reactions and Concepts

Flashcards on reaction types, homologous series, combustion, and halogen reactivity.

Substitution Reaction

A reaction where a hydrogen atom is replaced by another atom.

Addition Reaction

A reaction where two reactants, one of which is unsaturated, react with another molecule to form a single product.

Homologous Series

• each successive member differs by a CH2 group

• same general formula, same functional group

• shows a trend in boiling point and viscosity as the number of carbons increases.

Test for Alkenes

Add aqueous orange bromine to the solution. If alkenes are present, the orange bromine decolourises from orange to colourless. If alkenes are not present, it remains orange.

Complete Combustion

The reaction of an alkane or alkene with oxygen to produce carbon dioxide and water (Alkane/Alkene + O2 → CO2 + H2O).

Incomplete Combustion

The reaction of an alkane or alkene with insufficient oxygen to produce carbon monoxide and water (Alkane/Alkene + O2 → CO + H2O).

Reason for Incomplete Combustion

Insufficient amounts of oxygen.

Why Alkenes Burn with Smokier Flame

Alkenes have a higher percentage of carbon compared to alkanes.

Condition for Substitution of Alkanes

UV light.

Rate of Substitution - Group 17

Down Group 17, the reactivity of halogens decreases. The more reactive the halogen, the faster the rate of substitution.

Elements higher up in Group 17 have a faster rate of substitution compared to elements lower in Group 17.

Alkane gen form

CnH2n+2

Alkene gen form

CnH2n

why does mp and bp of alkanes increase as number of carbons increase

as size of molecule increases, imfoa become stronger, thus more energy is needed to overcome these bonds

why does viscosity of alkanes inc as no. of carbon inc

long carbon chains are more likely to get tangled together and flow less easily

why does flammability decr. as no. of carbon inc.?

Molecules evaporate less easily as they get larger

As percentage of C in the alkanes inc, the flame becomes sootier

Smoky flame is caused by incomplete combustion of the carbon

condition for alkene to react with hydrogen

nickel catalyst at high temp and pressure

what happens when alkenes react with hydrogen (with conditions met)

produces alkanes

what addition method is used to make margarine

addition of alkenes with hydrogen

how is margarine made?

addition of hydrogen;

Hydrogen added to polyunsaturated liq. veg. oils to form solid margarine

When H2 gas bubbled thru these oils, in presence of nickel catalyst and at high temp and pressure, the oils solidify as they become saturated

uses of polyethene

making plastic bags

cling wrap/film to wrap food

alkenes undergo what to form alcohols?

alkenes addition with excess steam at high temp and pressure and H3PO4 catalyst to form alcohol

conditions for forming of alcohols

high temps, pressure, presence of H3PO4 catalyst