UNIT 10 - Organic Chemistry Flashcards
State which nucleophilic substitution mechanism occurs at a faster rate.
Sn1 proceeds more quickly than Sn2.
State what colour is an alkane and an alkene under the influence of bromine water.
alkene - colourless
alkane - brownish
State the reagents needed to convert nitrobenzene into phenylamine.
- Tin and concentrated hydrochloric acid.
- Heated under reflux in a boiling water bath.
- Phenyl ammonium ions reacted with sodium hydroxide.
Distinguish between oxidation of primary alcohols if the desired product is aldehyde vs carboxylic acid.
aldehyde - mixture warmed gently and the aldehyde is distilled before it is further oxidized.
carboxylic acid - mixture is first heated under reflux with an excess of the oxidizing agent until all of the alcohol is converted into the carboxylic acid with the pure product obtained by distillation.
State the most common addition polymers and their industrial names.
Polychloroethene - PVC
Polytetrafluoroethene - PTFE, Teflon
Define the nitration of benzene.
Substitution of -H by -NO2 to form nitrobenzene C6H5NO2 using nitrating mixture (concentrated nitric and concentrated sulfuric acid).
Define configurational isomerism.
Can be interconverted only by breaking covalent bonds (cis/trans & optical).
State the two circumstances under which the cis/trans isomers arise.
- double bonded molecules - free rotation not possible because it would push the p orbitals out of position and the pi bond would break.
- cyclic molecules - ring restricts rotations and the bond angles are already strained.
Describe the mechanism of the Sn2 reaction with its molecularity and characteristic features.
Substitution nucleophilic bimolecular mechanism.
Involves a primary halogenoalkane attacked by a nucleophile
Forms a transition state where the carbon is weakly bonded to both the halogen and nucleophile
then the carbon-halogen bond breaks heterolytically releasing the halogen and forming the alcohol product inversion of the arrangement of the atoms around the carbon atom.
Define and state the reaction formula for esterification.
Reaction of alcohol with carboxylic acid in the presence of an acid catalyst (concentrated sulfuric acid) to form an ester and water.
ROH + R’COOH -H+-> R’COOR + H2O
Define homolytic fission.
A bond breaks by splitting the shared pair of electrons between the two products and thus produced two free radicals, each with an unpaired electron.
State the reducing agents for the reduction of carboxylic acid and a ketone.
carboxylic acid - LiAlH4 - lithium aluminum hydride
ketone - NaBH4 - sodiumborohydride
Define stereoisomerism.
Different spatial arrangements of atoms in molecules.
Define a carbocation.
Positive ion with the charge centered on a carbon atom.
State the utility of bromine water.
Used to distinguish between saturated and unsaturated compounds.
Define the steric hindrance.
A bulky molecule (with multiple bonds to compounds or groups other than hydrogen) slowing down or preventing another molecule from efficiently finding the desired bond site in a reaction.
State the product and catalyst of an alkene reacting with hydrogen.
Alkane (through hydrogenation)
nickel catalyst
150 degrees Celsius.
List the rules of the priority of substituents in cis/trans isomers.
- atom bonded to the carbon of the double bond with higher atomic mass has the higher priority.
- same rule to the next bonded atom if the atoms bonded first are the same (longer hydrocarbon chains have higher priority).
Define a structural isomer.
The same molecular formula with different arrangement of atoms.
Describe the electrophilic substitution in benzene.
Electron deficient species (electrophiles) are attracted to the electrons above and below the benzene ring and so can substitute the H atoms without needing to overcome the delocalization energy.
What properties will increase up (with increasing carbon number) the homologous series of compounds.
- boiling point - instantaneous induced dipoles and thus stronger LDF
- density
- viscosity
Define conformational isomerism.
Interconverted by free rotation about sigma bonds.
State the hybridization and angle of the carbon atoms in benzene.
120 degrees
sp2
Define a heterolytic fission.
Bond breaking with both the shared electrons going to one of the products.
Producing two oppositely charged ions.
State the product of an alkene reacting with a hydrogen halide (HCl/HBr).
halogenoalkanes
State the general reactivity of alkanes and mention the reactions they undergo.
Very unreactive.
- combustion
- free-radical substitution with halogens to form halogenoalkanes.
Define the addition polymers and list example.
Polymers formed from several thousand alkene monomers under certain conditions (e.g. high pressure)
polyethene H2C=CH2
State the product of a polymerization reaction of ethene.
polyethene
Distinguish between the primary, secondary and tertiary alcohols.
Primary - 1R group attached to the carbon atom
Secondary - 2R groups attached to the carbon atom
Tertiary - 3R groups attached to the carbon atom
Same rule for halogenoalkanes and amines.
State the functional group, its name, the suffix and the general formula for ketones.
R-C=O
R’-carbonyl-anone
R-CO-R’