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inorganic y2 / s1 > lecture 3 > Flashcards

lecture 3 Flashcards

1
Q

gemdiols dehydrate to give what

A

gemdiols dehydrate to give ketones

R R OH OH –> R R =O

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2
Q

covalent component depends mainly on what

A

the atom size and electronegativity

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3
Q

strong covalent bonds and orbital explanation

A

small atoms can approach each other closely providing good orbital overlap

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4
Q

why are covalent bonds weaker with NOF

A

bc the atom size is so small due to high electronegativity,, their lone pairs repel which reduces the amount of efficient orbital overlap

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5
Q

how electronegativity, size, overlap and bond strength change going down the group

A

down a group = lower electronegativity

= larger atomic size

= weaker overlap of orbitals

= weaker bond

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5
Q

electronegativity and bond energy..
at the top of the group // going to the rhs

A

larger electronegativity (not NOF) = smaller atom size = efficient orbital overlap = stronger bond

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6
Q

bond energies downa group

A

decrease

less energy
as atom gets bigger

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7
Q

when is pi bonding preferrred

A

with small atoms with small radii as it allows for orbitals to get closer and for effective overlap.

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8
Q

when is pi bonding particularly strong

A

non metals of the second period

BCNOF

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9
Q

when is pi bonding seen less

A

with atoms further down a group

with heavier atoms

bc theyre larger and more diffuse = large interatomic separation = poor overlap

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10
Q

gemdiols dehydrate to give what

A

dehydrate to give ketones

RR OH OH —-> RR =O

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11
Q

sometimes sigma bonds are preferred due to what + give an example

A

sigma bonds are preferred due to ionic interactions

Si-Si (220 kjmol)
Si - O (450kjmol)

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11
Q

gem silan diols dehydrate to give

A

Si - O - Si bridges

SOS but Si bc silan

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12
Q

when is pi bonding weaker between elements

A

pi bonding is weaker between 2nd and 3rd row elements due to their orbitals’ sizes + energy being differen.

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13
Q

for ionic systems,, what is a key factor

A

lattice energy stabilisation is a key factor as lattice energies can be much higher than that of covalent bonds.

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14
Q

entropy and which systems we need to avoid

A

for great stability we need to avoid systems where small molecules can be formed. WHEN IT IS WARMED!!!

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15
Q

do open chains or rings have more degrees of freedom

A

open chains have a higher degree of freedom (bc more units in the open chain: 3N)

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16
Q

what will entropy favour at elevated temps

A

entropy will favour ring opening

  • but there diff is a balance between TS and H needed to break the bonds of the ring when u ring open it
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17
Q

what factors indicate the stability of a compound

A

thermodynamic factors

but we can also consider kinetics

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18
Q

why should we consider kinetics

A

bc there are many compounds with are intrinsically unstable with respect to their elements but the Ea needed for decomposition to occur is too high.

eg: decomposition is inhibited.

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19
Q

why can a silicone ketone not occur

A

bc there isnt efficient overlap between the Si and the O

the pi bond would be too weak.

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20
Q

what makes a ketone a possibility when u go from gemdiol to ketone by releasing water

A

bc the C and the O are similar sizes so the pi bond has efficient overlap

bc theyre both at the top of the group.

21
Q

larger r groups likeeee

A

smaller rings

22
Q

name some small groups which can be released when a reaction is warmed

A

N2
CO2
H2O
HCl
NO

23
Q

why can decomposition be inhibited even if the compound is intrinsically unstable

A

bc sometimes the Ea needed for the reaction to take place is too high.

the decomposition product may be more stable,, but the reactant may have stronger bonds

24
Q

how can decomposition occur to main group rings and chains

A

via electrophilic // nucleophilic attacks

25
Q

increasing stability: what must we avoid in order to prevent coordination with a reactive donor,, a nucleophile

A

we must avoid low energy acceptor orbitals

26
Q

improving stability: what do we do if the compound has a reactive acceptor

A

bulky substituents can prevent an attack by a nucleophile

27
Q

improving stability: what can we use to reduce the ability of the reactive centre to act as a lewis acid // base

A

we can use EDG and EWG and their properties - these are already bonded to the central atom and affect its reactivity towards attackers

28
Q

lewis acid issss

A

accepts e- pairs from a lewis base to form an adduct

29
Q

lewis base

A

donates e- pairs to a lewis acid in order to form an adduct

30
Q

adduct

A

basically just the product of 2 things bonding together to form a new molecule. this has all the atoms from each reactant species.

31
Q

what do EWG and EDG do to the reactive centre atom

A

they affect its reactivity - either making it a poorer donor or a weaker acceptor

32
Q

where are multiple bonds between elements containing a valence 2p orbital common

A

top of the 2p block

C N O etccc

33
Q

when are multiple bonds between elements containing valence 2p orbitals not common

A

with heavier atoms

further down the 2p block,, double bonds are seen less here compared to the upper p block elements like c n o

34
Q

why are multiple bonds (triple and double) not seen as much further down the p block (valence 2p orbitals)

A

larger atom size
more diffuse orbitals
less efficient overlap
weaker pi bondssss

35
Q

why are multiple bonds (double and triple) seen more in the atoms closer to the top of the 2p block - ones with valence 2p orbitals

A

smaller atom
smaller radii
less diffuse orbitals
more efficient overlap
stronger pi bondsss

36
Q

as heavier atoms with a valence 2p orbital dont form multiple bonds as much due to their size and weak overlap,, what do they form?

A

oligomers

they max out their single bonds

37
Q

what is an oligomer

A

a polymer with only a few repeating units

sigma bonds are maximised

38
Q

what overlap do the larger 2p orbitals lack,, preventing them from forming pi bonds

A

they lack spatial overlap

39
Q

what is spatial overlap girll

A

the pi bond side overlap 🫶

40
Q

C=C shape

A

planar shape

41
Q

Sn = Sn shape

A

trans bent

aka lhs R groups tilting down (one wedge and one dashed)

aka rhs R groups tilting up (one dashed and one wedge)

42
Q

is the Sn=Sn stronger than C=C

A

nope
C=C is stronger
more efficient spatial overlap bc the atomic radi is smaller

43
Q

why does Sn = Sn adopt a trans bent structure

A

to try and form the most stable sigma bond

44
Q

unhybridised p orbitals overlap to give what

A

unhybrid p orbitals overlap to give pi bonds

45
Q

hybridised p orbitals overlap to give what

A

sigma bond

46
Q

how can we rationalise bent structures

A

break them through the middle and see how they associate

47
Q

breaking the C=C planar shape down thr middle will give what : explain it and where the e- would be

A

2 Cs with 3 hybridised orbitals and 1 unhybridised p orbital

C will have both aligned up,, one in the unhybridised orbital,, and one in the hybridised orbital (ONE IN THE HYBRID THAT FORMS THE SIGMA,, ONE IN THE ORBITAL THAT FORMS THE PI)

the other C will be the same in terms of e- but the e- will be aligned down

48
Q

C has 4 e- so when we break the pi bond in the centre,, where will all the e- be

A

1 in unhybridised orbital
1 in hybridised orbital
1 in the R group bond
1 in the other R group bond

49
Q

explain how we break the Sn =Sn bond and how they both associate

A

basically the same thing as the C,, it will have 3 hybridised orbitals which are bonding to 2 R groups and one will have 2 e-,, a pair if u will.

the 2e- in the hybrid orbital will donate these to the unhybridised + vacant p orbital of the other Sn

it gives a dative bond type vibe

50
Q

describe what the triplet state looks like + if C or Sn prefer this

A

Carbon is more stable in the triplet state

this is where one C has them aligned up and the other C has them aligned down. but the e- are unpaired and 1 is in the hybrid and 1 is in the unhybrid p orbital.

spin = 1 bc theyre both looking up,, and theyre 1/2 each.

51
Q

describe the singlet state,, what it looks like and if C or Sn prefers it when we break the double bond

A

singlet state is when the e- pair is in one of the hybrid orbitals

with R groups on the other hybrids

and with the vacant p orbital

inorganic y2 / s1 (10 decks)

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