unit 4 aos 1 chem

what is a catalyst? what the advantages of a catalyst?

catalysts increase the rate of reaction by decreasing the activation energy which reduces energy consumption and greenhouse gas production.

• catalysts can be used continuosly therefore less reagants are used and better atom economy

why do different functional groups require different environmental conditions (catalyst, heat)?

• different functional groups have to overcome various activation energies

• heat is used to overcome activation energy / increase the rate of reaction

• the catalyst is used to decrease the activation energy

what are functional groups for carboxylic acid, ketones, aldehyde, amine, amide, alcohol, ester?

carboxylic acid (carboxyl)

ketone / aldehydes (carbonyl)
amine (amino)
amide (amide)
alcohol (hydroxyl)
ester (ester)

why is the melting/boiling point of alkenes lower than alkanes?

• alkenes have a lower boiling point because it forms a permanent kink in its molecular strcuture and as a result, molecules are unable to pack as tightly

• this decreases the strength of dispersion forces

• as a result, less energy is required to vibrate and break the intermolecular bonds, resulting in lower boiling/melting point than alkanes

what is the order of intermolecular forces? strongest to weakest and polarity

• hydrogen bonding (polar molecules)

• dipole - dipole interactions (polar m

• dispersion forces (non - polar molecules)

what is the order of melting/boiling point for different classes and why? highest to lowest

amide - h bonds - multiple hydrogen bonds can form between the NH and CO groups

carboxylic acid - hydrogen bonds - forms dimers which increases strength of molecular forces

alcohol - hydorgen bonds - higher than amines because the oxygen atom is more electronegative than the nitrogen atom

why is there a high boiling point?

physical properties

• higher molar mass

• more electrons

• longer carbon chains - greater dispersion forces

• straight chained branching - can pack together more tightly

structure and bonding

• hydrogen bonding - dimers

• hydrogen bonding

• dipole - dipole interactions

• dispersion forces

what does it mean when a molecule is saturated and unsaturated

saturated - molecules that have C-C single bonds

unsaturated - moslecules that have C=C double bonds

what are the 3 types of structural isomers?

positional isomer - the functional group occurs in different positions

functional isomer - same molecular formula but different functional groups

chain isomer - different chain arrangements and branching

out of primary secondary and tertiary alcohols, what has the higher BP?

tertiary alcohols have a lower BP. tertiary alchols have a lower BP because it is ‘crowded’ by alkyl groups which restricts the hydroxygl group from forming hydrogen bonds with other molecules. thereby having a lower BP than primary and secondary alcohols

why is the boiling point of alcohols greater than the boiling point of amines?

pxygen is more electronegative than nitrogen

• the electrostatic attraction of the hydrogen bond is stronger when oxygen is involved

• since alcohols have hydroxyl bonds with oxygen atoms, their hydrogen bonds are stronger than amines, which have amino groups with nitrogen atoms

why do carboxylic acids have the highest boiling point?

carboxylic acids are polar molecules which has hydrogen bonds and forms dimers which increases the strength of dispersion forces. more energy is required to break the intermolecular forces, leading to carboxylic acids to have a high boiling point

• hydrogen bonding (polar molecules)

• forms dimers which increases the strength of dispersion forces

• more energy is required to break the intermolecular forces