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Chem@York Core 1 > Organic Reactions and Mechanisms > Flashcards

Organic Reactions and Mechanisms Flashcards

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1
Q

What does the iPr abbreviation mean?

A

Isopropyl, propyl where the chain is bonded to the centre carbon

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2
Q

What does the abbreviation tBu mean?

A

Tertiary butyl, a carbon with 3 methyl groups

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3
Q

What is the definition of functional group number?

A

The number of bonds to heteroatoms from a given carbon atom

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4
Q

What is the difference between a phenol and a thiol?

A

A phenol is an -OH group bonded to an aromatic ring, a thiol is an -SH group

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5
Q

What is an epoxide?

A

An oxygen atom bonded to 2 carbons which are also bonded together. This produces a very strained ring with bond angles of 60°

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6
Q

What is a peroxide? Why are they so reactive?

A

A -O-O- functional group, the O-O bond is very weak

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7
Q

What is an aromatic amine called?

A

An aniline

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8
Q

What is unusual about the nitro group?

A

It has a positively charged nitrogen group and a negatively chafed oxygen group

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9
Q

How do you work out formal charge?

A

Group number - unshared electrons - 1/2 electrons in bonding(from any atom)

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10
Q

What is a hydrate?

A

A carbon with 2 -OH groups

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11
Q

What is an acetal and a hemi-acetal?

A

A carbon with 2 -OR groups, a carbon with an -OR and a -OH group

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12
Q

What is an imine and an oxime? Why are they uncommon?

A

A -C=N-R group and a -C=N-OH group. Because they are very reactive

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13
Q

What is an anhydride group?

A

R-C(=O)-O-C(=O)-R

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14
Q

What is a carbonate group?

A

R-O-C(=O)-O-R

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15
Q

What is a carbamate group?

A

R-O-C(=O)-NH-R

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16
Q

What is an urea group?

A

R-NH-C(=O)-NH-R

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17
Q

What is an isocyanate group?

A

R-N=C=O

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18
Q

How do you increase functional group level?

A

Oxidation (loss of hydrogen)

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19
Q

How do you decrease functional group number?

A

Reduction (gain of hydrogen)

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20
Q

What part do pi bonds take in functional group number?

A

Each pi bond bond increases function group number by 1, this means an alkyne has 2 carbons with a functional group number of 2

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21
Q

What is the -CN group called?

A

Nitrile

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22
Q

What is better, relatively stable or reactive intermediate?

A

Relatively stable as this lowers the activation energy which increases the rate of the reaction

23
Q

What is the definition of a mesomeric effect?

A

The movement of electron density within a double bond (pi) system of a molecule by resonance conjugation

24
Q

What M effect is -C(=O)-R?

A

-M

25
Q

What M effect is -CN?

A

-M

26
Q

What M effect is -NHR?

A

+M

27
Q

What M effect is -OH?

A

+M

28
Q

What M effect is -Cl? Describe its strength

A

+M, weak as its 3p orbital has poor overlap with the 2p orbital

29
Q

True or false, can elements expand their octet to aid mesomeric effects?

A

No, elements such as oxygen and carbon never have less than 8 electrons in their valence shell

30
Q

Are double bonds and aromatic rings +M or -M?

A

Either, they will resonate with a positive or negative charge

31
Q

Why can resonance occur between functional groups when they are in para and ortho positions on an aromatic ring but not in the meta position?

A

There has to be a ‘cascade’ of electrons, in the meta position this is not possible

32
Q

Why are methyl groups +I?

A

A hydrogen carbon bond can line up(badly) with an empty p orbital in on an adjacent bond to give some pi overlap

33
Q

What is the word for when 2 parts of a functional group could react, but only one does?

A

Regioselectivity

34
Q

What does the last number in Sn1 and Sn2 mean?

A

How many reactants are in the rds

35
Q

In an Sn2 mechanism, how does the stereochemistry change?

A

The nucleophilic attacks from behind the C-E bond and pushes the other groups round, this is called the Walden inversion

36
Q

What does R and S stereochemistry mean?

A

R is when a chiral centre has the largest to smallest groups going clockwise (right from 12), S is the opposite (S=sinister=left from 12)

37
Q

Why are 2 products formed from the Sn1 reaction?

A

The intermediate is sp2 hybridised so the nucleophile can attack from either side of the planar intermediate

38
Q

Why won’t nucleophiles react with small aromatic compounds?

A

The negative electrophile will be repelled by the delocalised cloud of electrons

39
Q

What 4 factors affect which Sn mechanism is favoured?

A
  1. Carbocation stability
  2. Nucleophile
  3. Leaving group
  4. Solvent
40
Q

Which mechanism does a stable carbocation favour?

A

Sn1

41
Q

What 2 factors affect the strength of a nucleophile and which mechanism will they favour?

A
  1. Size, a small nucleophile will increase its reactivity and will favour Sn2
  2. Ability to share electrons, the more electronegative an atom is the less likely it is to share its lone pair as a nucleophile, more electronegative favours Sn1
42
Q

What 2 factors affect the ability of a leaving group and which mechanism will it favour?

A
  1. The strength of the leaving groups bond, the weaker the bond the better the leaving group, this will favour Sn1
  2. The stability of the leaving group, the more stable, the better, this will favour Sn1 e.g. Neutral species are better leaving groups than charged groups
43
Q

Which solvents will favour Sn1 mechanisms and why?

A

Polar, protic solvents such as water, methanol and ethanoic acid as they stabilise charged species and hydrogen bonds can interact with anions

44
Q

Which solvents favour Sn2 mechanisms?

A

Polar, aprotic solvents such as Me2-S=O (DMSO) and ethanenitrile as they stabilise the the charged species but have no hydrogen bonds to interact with the nucleophile

45
Q

If a product has its methyl (or hydride) swapped in a product what has happened?

A

To stabilise a positive charge, a methyl (or hydride) group has swapped carbons

46
Q

If a nucleophilic substitution reaction has occurred but the stereochemistry has not been altered what could have happened?

A

Either an Sn1 reaction has occurred or an internal nucleophile has reacted with itself before the nucleophile (2 Sn2 reactions will cancel the Walden inversion out)

47
Q

What is chemoselectivity?

A

Where one potential reactive site reacts in preference to other possibilities

48
Q

What is more nucleophilic, iodide or fluoride and why?

A

Iodide as its electrons will make bonds much more readily than the more electronegative chlorine

49
Q

Which is more nucleophilic, NH2 or OH and why?

A

Nitrogen as it is less electronegative so it won’t hold onto its electrons so much

50
Q

Why will molecules with the leaving group attached to a tertiary carbon almost always follow a Sn1 mechanism?

A

There’s no room for a nucleophile to attack because the alkyl chains crowd the point the nucleophile wants to attack

51
Q

Order in terms of reactivity; esters, ketones and aldehydes, explain the order

A

Aldehyde>ketone>ester

Esters have mesomeric effects, ketones have the +I effect of 2 alkyl groups, aldehydes only have 1 +I alkyl group

52
Q

What 2 factors make a conjugate base stable, therefore making the site acidic when protonated?

A

The negative charge on an electronegative atom and the charged species conjugated. +I effects will also help.

53
Q

What 2 factors will make a site more basic?

A

Lone pairs/negative charges localised (no conjugation), the less electronegative the species donating electrons

Chem@York Core 1 (9 decks)

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