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AECHE > cap 4 - organic chemistry and reaction rates > Flashcards

cap 4 - organic chemistry and reaction rates Flashcards

1
Q

why is carbon able to form such a diverse range of compounds?

A

2, 4 electron configuration (4 valence) ⇒ ability to covalently form 4 more single bonds ⇒ variety of arrangements (single, double, triple) ⇒ forms many compounds

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2
Q

hydrocarbons

A

organic compounds, based on hydrogen and carbon atoms

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3
Q

aliphatic

A

carbon atoms arranged in open chains ⇒ can be saturated or unsaturated

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4
Q

aromatic

A

carbon atoms arranged in closed rings

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5
Q

functional groups

A

atom or group of atoms responsible for typical chemical reactions, determining patterns of reactivity

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6
Q

homologous series

A

group of molecules with same functional group, but different number of carbons in the main chain

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7
Q

alkanes

A

single bonds only
saturated compounds
C(n)H(2n+2)

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8
Q

alkenes

A

at least one double bond
unsaturated compound
C(n)H(2n)

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9
Q

benzenes

A

unsaturated hydrocarbon of a perfectly hexagonal, flat ring structure consisting of 3 double and single bonds (rapid equilibrium model), and a cloud of delocalised electrons above and below the ring; colourless liquid at room temp

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10
Q

formula for cycloalkanes

A

C(n)H(2n)

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11
Q

formula for cycloalkenes

A

C(n)H(2n-2)

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12
Q

saturated hydrocarbons

A

consisting of only single bonds (bonded to the maximum number of hydrogens)

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13
Q

unsaturated hydrocarbons

A

consisting of at least one double or triple bond, thus being more reactive (double bond broken to accommodate addition of more hydrogen atoms)

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14
Q

isomerism

A

same molecular formula but a different spatial arrangement (structural or geometrical)

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15
Q

structural isomerism

A

varying physical structure (can be chain, positional, functional group)

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16
Q

chain isomerism

A

consisting of branches and additional substituents

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17
Q

substituents

A

additional “branches” or “stems”, named as according to where they are and how many carbons they have

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18
Q

positional isomerism

A

location of double bonds

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19
Q

functional group isomerism

A

location of functional groups

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20
Q

geometrical isomerism (cis-trans)

A

structural rotations around C-C double bonds

21
Q

sigma bonds

A
  • single bonds, strongest out of all bonds
  • rotational symmetry (NO geometrical isomerism)
22
Q

pi bonds

A
  • double or triple bonds
  • weaker and more reactive
    • rotation causes weaker bond to “snap” or break
    • has different symmetry (geometric isomerism)
  • much more electron deficient ⇒ much more susceptible to reactions
23
Q

reactivity of hydrocarbons

A

unsaturated hydrocarbons are MORE reactive than saturated hydrocarbons;

for alkanes to react, highly stable sigma bonds must be broken (requiring large amounts of energy to break the stronger bonds) ⇒ large input energy ⇒ relatively higher activation energy ⇒ lower rate of reaction ⇒ lower reactivity

24
Q

substitution reactions

A

type of chemical reaction where an atom or functional group of a molecule is replaced by another atom or functional group

25
Q

substitution of alkanes (energy)

A

UV light supplies sufficient energy to meet the activation energy of the reaction => breaking bonds between halogens (diatomic molecules) => atoms in high energy state can react with alkane to substitute with hydrogen

26
Q

substitution of benzenes (catalyst)

A

halogens involved in substitution aren’t electrophilic enough to break the aromatic nature of benzene, so a catalyst is used to attract electrons for substitution

e.g. nickel catalyst for hydrogenation

27
Q

addition reaction

A

type of chemical reaction where atoms are added across the double bond of an alkene to form an alkane or a substituted alkane, breaking pi bond to form another sigma bond

28
Q

why do addition reactions happen so quickly

A

sigma is stronger and more energetically favourable to form, being more stable, so weaker pi bond will more readily break to form a stabler sigma bond

29
Q

test for unsaturation

A

add few drops of bromine water (orange) or iodine water (brown) into the tested liquid, and shake

two layers would form, since nonpolar hydrocarbons are insoluble in the polar solution (halogens bottom layer)

if unsaturated, would undergo addition reaction and decolorise

30
Q

complete combustion reactions

A

hydrocarbon + excess oxygen → carbon dioxide + water + energy

31
Q

incomplete combustion reactions

A

hydrocarbon + insufficient oxygen → carbon monoxide + water + energy

hydrocarbon + insufficient oxygen → carbon + water + energy

less exothermic than complete combustion, i.e. releasing lots of energy per unit; soot is air pollution, carbon monoxide is poisonous gas

32
Q

pressure

A

force exerted per unit area by collisions between gas particles and interior surfaces of container (gases consist of particles in constant random motion), measured in pascals (Pa)

33
Q

temperature

A

measure of average molecular kinetic energy

34
Q

activation energy

A

minimum amount of energy required for particles to react

minimum amount of energy required to form the activation complex

(energy needed for the bonds of the reactants to break)

35
Q

transition state (activation complex)

A

state corresponding to the highest potential energy (particular configuration) along the reaction coordinate

activation complex = temporary, highly unstable formation (bonds of reactants broken, bonds of products not yet formed)

36
Q

collision theory

A
  • reactants must collide
  • with sufficient, activation energy
  • at appropriate orientation
37
Q

rate of reaction depends on

A
  • frequency of collisions
  • proportion of successful collisions
38
Q

rate of reaction

A

NUMBER OF SUCCESSFUL COLLISIONS OVER A GIVEN TIME

change in concentration of reactants or products per unit time (speed of reaction)

measured using indicators of reactions (mass, colour, volume, pH, concentration) => volume of gas produced, loss of mass, change in transparency

slows over time (concentration of reactants decreases, reduced frequency of collisions)

39
Q

key factors for rate of reaction

A

temperature
surface area
volume / pressure
presence of catalysts
concentration

40
Q

concentration of dissolved reactants

A

higher concentration ⇒ more particles in the same amount of space ⇒ increased frequency of collisions, same proportion of collisions that are successful ⇒ more successful collisions (same chance but more collisions)

41
Q

pressure of gaseous reactants (volume of container)

A

decreased volume, increased pressure ⇒ smaller space for gas particles, closer together ⇒ increased frequency of collisions, same proportion of collisions that are successful ⇒ more successful collisions (same chance but more collisions)

42
Q

surface area of solid reactants

A

(all reactions with solids occur on the surface) split into several pieces ⇒ increased surface area ⇒ increased area for reactants particles to collide with ⇒ increased frequency of collisions, same proportion of collisions that are successful ⇒ more successful collisions (same chance but more collisions)

43
Q

temperature

A

higher temperature ⇒ higher average kinetic energy of particles

increased average velocity of particles ⇒ increased frequency of collisions ⇒ more successful collisions (same chance but more collisions)

colliding with more energy (increased number of collisions having sufficient activation energy) ⇒ increased proportion of collisions that are successful

44
Q

catalyst

A

a substance that speeds up a chemical reaction without being consumedz

45
Q

presence of a catalyst

A

offers an alternate pathway for the reaction with a lower activation energy, without directly lowering the activation energy

greater proportion of collisions have sufficient energy to overcome activation energy and form transition complex ⇒ greater proportion of successful collisions

46
Q

maxwell-boltzmann distribution curve

A

demonstrates the proportion of particles that are expected to successfully undergo a collision and thus a chemical reaction

47
Q

sources of error for gas experiment (inverted cylinder)

A

(random) state of subdivision and surface area : volume ratio of marble chips

(random) parallax error in reading inverted measuring cylinder

(systematic) loss of gas produced; systematic delay of placing stopper

(systematic) loss of gas by dissolution in water

48
Q

sources of error for “cross” concentration experiment

A

(random) parallax error, dependent on perception, to determine when cross disappears

(systematic) “degree” of swirling, where agitation increases frequency of collisions

(systematic) human reaction time

49
Q

sources of error for the “cross” temperature experiment

A

(random) parallax error, dependent on perception, to determine when cross disappears

(systematic) “degree” of swirling, where agitation increases frequency of collisions

(systematic) calibration of the water bath, assuming exact temperature of thermometer

(systematic) temperature lost to surrounds

(systematic) human reaction time

AECHE (8 decks)

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