Organic chemistry AS level CIE

Stereo - isomerism

Isomerism arising from differences in the shapes of the molecules. Includes geometric and optical isomerism

Condensation reaction

Reaction in which two molecules join together with the loss of a small molecule, typically water.

Fission, heterolytic

Bond breaking in which the more electronegative of the two atoms joined by the bond takes both of the electrons.

Write an equation for the reaction between methane and chlorine to form chloromethane. Explain this reaction in terms of a free-radical mechanism.

CH4 + Cl2 → CH3Cl + HCl hv/uv light Initiation step: Cl2 → 2Cl•; hv/uv light Propagation step: CH4 + Cl• → CH3• + HCl; CH3• + Cl2 → CH3Cl + Cl•; Termination step: Cl• + Cl• →light Cl2 or Cl• + CH3• → CH3Cl or CH3• + CH3• → CH3CH3;

Optically active

Can rotate the plane of polarization in opposite directions. Enantiomers are optically active

Addition polymerisation

Forming a polymer by addition of monomers

Condensation polymerisation

Forming a polymer by substitution reaction between monomers, each having two functional groups

Electrophiles

positively charged species that are attracted to high concentration electron environments

Functional Group

-An atom or group of atoms (other than hydrogen) -Impacts specific physical and chemical properties of a homologous series of organic compounds.

Which compound forms when hydrogen bromide is added to but-2-ene? A. 2-bromobutane B. 2,3-dibromobutane C. 1-bromobutane D. 1,2-dibromobutane

A. 2-bromobutane

Hydrolysis

Process by which a molecule is broken down by water

Esterification

Process by which an alcohol and a carboxylic acid are converted into an ester and water, often with acid catalysis.

Dehydration

Loss of water. Alcohols can be dehydrated when they are refluxed with condensed sulphuric acid. As sulphuric acid is an oxidizing agent able to react with the product, phosphoric acid is frequently used instead

Molecular Formula

The actual number of atoms in a compound

Empirical Formula

The lowest whole # ratio of atoms in a compound

Homologous Series

The series of hydrocarbons that follows the formula C(n)H(an+b)

Reaction Mechanism

The series of steps needed to go from reactants to products within an organic reaction

Substitution reaction

When an H on the carbon chain is switched out for a substituent group or functional group

Addition Reaction

When two organic compounds are added together to make a singular compound. Involves increasing the size of the carbon chain

Chain Reaction

when a small event causes many subsequent events to occur

Termination

when the # of free radicals DECREASE

Initiation

when the # of free radicals INCREASE

Propagation

when the # of free radicals STAY CONSTANT

Reaction, condensation

A reaction in which one group is substituted for another. Substitution reactions with halogenoalkanes are nucleophilic substitutions.

Sigma bond

-pair of electrons if found in a region in space between the two atoms sharing electrons -attracton btween +vely charged nuclei and -vely charged electrons bonds atoms together -commonly carbon forms 4 sigma bonds -4 bonding pairs of e- around C are repelled by each other as far apart as possible -tetrahedral - 109.5°

Structural isomers

-same molecular formula -different structural formula 3 types: 1)Position isomerism 2)Functional group isomerism 3)Chain isomerism

Pi bond

-within double bonds -C atoms in double bond will each form 3 σ bonds, leaving each C atom with 1 spare e- in 2p orbital -the overlap of two 2p orbitals forms a π bond -the position of the electrons is above and below the plane of atoms, which maximises the overlap -the C atoms involved in the double bond are each surrounded by 3 pairs of e- in the σ bonds = repel each other to 120°

Mechanism, SN2

A bimolecular process by which a halogenoalkane undergoes nucleophilic substitution. Mechanism involves formation of a transition state which involves both of the reactants.

Carbocation

A cation in which the carbon carries most of the + charge. Can be formed during SN1 substitution.

Isomer/Structural Isomer

A molecule with a different structure but the same chemical formula

Reaction, addition

A reaction in which the reactant is added across a C=C bond, converting it to a C-C bond. Addition reactions with water requires an H2SO4 catalyst. Addition reactions with hydrogen use Ni as catalyst.

Structural formula

A structural formula shows the connectivity of the atoms in the molecule.

Mechanism, SN1

A unimolecular process by which a halogenoalkane undergoes nucleophilic substitution. A two-step mechanism: a rate-determining step in which the bond between the carbocation and the halogen are broken, followed by a step in which the nucleophile is attracted to the carbocation. Faster than SN2, as the formation of the intermediate carbocation is faster than the SN2 route which involves a transition state with relatively high activation energy.

Catenation

Adding carbons to chain

Hydration

Addition of water. Ethanol can be formed from addition of water to ethene.

Chiral center

An asymmetric carbon atom, i.e. has four different functional groups attached to it.

Free Radical

An unbonded atom that can accept an extra electron to make a bonding pair

State and explain the trend in the boiling points of the first six alkanes involving straight-chains.

Boiling point increases as the number of carbons increases / OWTTE; Greater Mr and hence greater van der Waals'/London/dispersion forces present;

Fission, homolytic

Bond breaking in which each atom takes one of the electron in the bond, creating free radicals.

What is the organic product of the reaction between ethanol and ethanoic acid in the presence of sulfuric acid? A. CH3CHO B. CH3COOCH3 C. CH3CH2COOCH3 D. CH3COOCH2CH3

D. CH3COOCH2CH3

Nucleophilic substitution

Substitution that occurs with a halogenoalkane reacting with a nucleophile. Rate depends on: **nature of halogen atom **nature of halogenoalkane (tertiary > secondary > primary).

Steric Hinderance

The prevention or slowing down of a reaction by atoms or functional groups blocking the access of an attacking molecule or ion

Homolytic Fission

The process of braking apart one molecule to create two identical atoms or molecules that acts as free radicals