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organic 2 reactions > first part > Flashcards

first part Flashcards

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Organic Chemistry 101 flashcards
1
Q

types of bond breaking

A

heterolytic
homolytic

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2
Q

heterolytic bond breaking

A

when both electrons in a covalent bond go to one species.

2e- chemistry
ions form

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3
Q

homolytic bond breaking

A

when one electron goes to each species
1e- chemistry
radicals are formed

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4
Q

what is bond dissociation enthalpy

A

energy required to break a bond homolytically

the radical one

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5
Q

what does a high bde mean

A

its a strong bond
needs lots of energy to break it
poorly stabilised radicals

(lots of energy is needed bc the radicals dont want to be formed bc they will be poorly stabilised) 9hydrogen radical, methyl radical)

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6
Q

what does a low bde mean

A

little energy needed to break the bond homolytically
weak bond
well stabilised radicals ( tertiary structures, strong electrophilic radicals)

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7
Q

what is enthalpy change

A

heat given in or taken out by a reaction

we can estimate this using the bde values

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8
Q

breaking bonds require

A

energy
positive numbers

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9
Q

forming bonds dont require

A

energy
negative numbers

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10
Q

negative enthalpy value means the reaction is

A

exothermic

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11
Q

positive enthalpy value means the reaction is

A

endothermic

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12
Q

what is S

A

change in enthalpy
likes disorder
gas> solid
2 molecules>1 molecule.
higher S = higher entropy
snake in a tree
snakes like being in the leaves bc its more disordered than the trunk. larger s is more disordered as the leaves are higher off the ground than the bark

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13
Q

gibbs free energy equation

A

change in cG = cH -Tcs
kJmol-1 = kJmol-1 - K JK-1mol-1

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14
Q

what is an exergonic reaction

A

reaction where the products have less energy than the starting material

products are favoured at equilibrium

looks like exothermic reaction profile

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15
Q

what is an endergonic reaction

A

where the starting materials have lower energy than the products

starting materials are favoured at equilibrium

looks like endothermic reaction profile

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16
Q

in the endergonic and exergonic reaction profiles, what is the gibbs energy

A

height difference between the 2 lines of sm to p

17
Q

if G has a negative value,

A

its an exergonic reaction
products are favoured

18
Q

if G has a positive value,

A

its an endergonic reaction
sm are favoured

19
Q

equilibrium constant equation

A

conc of products / conc of reactants

20
Q

another change in gibbs equation kJmol-1

A

(- gas constant x temp) x ln(equilibrium constant)

21
Q

what does the value of gibbs free energy tell us

A

if sm or p are favoured at equilibrium

doesnt tell us about the rate.

22
Q

rate equation with differentials,, yk this girl!!

A

d(conc products)/d(time)

change in product conc/ change in time

23
Q

what is a rate equation eg

A

k [a] [b]

24
Q

[a] to the power of 1 means

A

first order
sn1
change of this is proportional to change in rate

25
Q

[a] to the power of 2 means

A

second order
sn2
change of this is proportional to double the change in rate

26
Q

what relates the rate constant and the activation energy

A

arrhenius equation

k = Ae ^ -Ea/Rt

27
Q

what is at the top of an energy curve

A

local maxima peaks
transition states
higher in enery
less stable

28
Q

what is a transition state

A

occurs during bond making / breaking
dotted arrow diagram
at local maxima peaks
higher in energy
cant be observed or isolated
transient species (not around for a long time)

29
Q

what is on the slightly lower parts of an energy curve diagram

A

intermediates
occur at local energy minima

30
Q

what is an intermediate

A

carbocation intermediate can be observed and isolated
lower in enery, more stable
bonds arent in the process of being formed or broken (no dotted lines but a + or -)
sn1

31
Q

what does it mean to be a transient species

A

to not be around for a long time

32
Q

how can a transition state be drawn

A

dotted line
square brackets
= sign with | in the middle in top right hand corner of the [ ]

33
Q

what is the hammond postulate

A

shows if the transition state is closer to the starting materials or the products

34
Q

hammond postulate for an exergonic reaction

A

Ts resembles starting materials as that line is closer to the local energy maxima peak.

35
Q

hammond postulate for endergonic reactions

A

Ts resembles products as the line for products is closer to the local energy maxima

organic 2 reactions (7 decks)

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