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CHEM 110 > Block 6 - Functional Groups 2 > Flashcards

Block 6 - Functional Groups 2 Flashcards

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1
Q

Alcohol - naming priority

A

Alcohol functional group takes priority for numbering the parent alkyl chain

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2
Q

Alcohol - solubility

A

Small alcohols (up to C5) water soluble

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3
Q

Alcohol - acid or base

A

OH group of alcohol, under appropriate conditions, has ability to react either as an acid or base
Formation of either conjugate base (alkoxide) or conjugate acid (oxonium ion) is usually the first step in reaction of alcohols

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4
Q

Alkyl halide hydrolysis

A

Nucleophilic substitution (SN1 or SN2)
Nucleophile: H2O or OH-
Forms alcohol

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5
Q

Acid catalysed addition of H2O to alkenes

A

Electrophilic addition
Nucleophile: H2O
Requires acid (usually H2SO4)

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6
Q

Hydroboration-oxidation of alkenes

A 
Anti-markovnikov's rule
Electrophilic addition (followed by oxidation)
Reagents: 1. B2H6, 2. OH-, H2O2 (reverses selectability, where most substituted = minor)
B added to least substituted end of C=C bond, and then replaced with OH
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7
Q

Reduction of aldehyde

A

Nucleophilic addition
Reagent: 1. NaBH4 or LiAlH4, 2. H3O+
Forms 1° alcohol

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8
Q

Reduction of ketone

A

Nucleophilic addition
Reagent: 1. NaBH4 or LiAlH4, 2. H3O+
Forms 2° alcohol

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9
Q

Reduction of ester

A

Nucleophilic addition
Reagent: 1. LiAlH4, 2. H3O+
Forms 1° alcohol

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10
Q

RMgX

A

Grignard reagent

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11
Q

Addition of RMgX to methanal

A

Reagent: 1. methanal, 2. H3O+

Forms 1° alcohol

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12
Q

Addition of RMgX to other aldehydes

A

Reagent: 1. aldehyde, 2. H3O+

Forms 2° alcohol

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13
Q

Addition of RMgX to ketones

A

Reagent: 1. ketone, 2. H3O+

Forms 3° alcohol

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14
Q

Addition of RMgX to Z (ester or acid chloride)

A

Reagent: 1. ester / chloride, 2. H3O+

2 equivalents of Grignard reagent + ester / acid chloride added –> 3° alcohol

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15
Q

Phenols

A

Hydroxy (OH) group directy bonded to sp2 C of an Ar

Weakly acidic, as the phenoxide anion (conjugate base) is resonance stabilised

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16
Q

Aromatic rings - the more delocalised a charge is…

A

The more stable a molecule is

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17
Q

The more stable the conjugate base…

A

The more acidic the parent acid

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18
Q

Aromatic ring substituents - Electron Withdrawing Groups vs Electron Donating Groups

A

EWG:
Increase acidity as they stabilise the phenoxide anion
Groups that are deactivating towards electrophilic aromatic substitution will be electron-withdrawing
EDG:
Decrease acidity, as they destabilise the phenoxide anion
Groups that are activating towards electrophilic aromatic substitution will be electron-donating

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19
Q

Faster way (than SN2) of converting (primary) alcohols to alkyl chlorides

A

SOCl2, with pyridine

SOCl2 is a more nucleophilic source of Cl

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20
Q

Alcohol - nucleophilic substitution - alcohol acts as…

A

The electrophile

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21
Q

Alcohol to ether

A

Alcohols/alkoxides act as nucleophiles in a substitution reaction to give an ether
O- of alkoxide reacts with R-Br –> OR + Br-

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22
Q

Elimination of alcohol

A

Reagent: conc H2SO4 + heat
1° alcohol - E2 mechanism; won’t be in competition with SN2 as HSO4- is a very weak base and no nucleophilic
2° alcohol - either E1 or E2 mechanism
3° alcohol - E1 mechanism (stable carbocation)

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23
Q

Alcohol - oxidation

A

Involves breaking C-H bonds and forming C-O bonds

For oxidation to occur, must be at least 1 H attached to the C –> tertiary alcohols can’t be oxidised

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24
Q

Alcohol: Oxidation - 1° alcohol to aldehyde or COOH

A

Reacting with H2CrO4 (strong):
ROH –> [RCHO] –> RCOOH
Reacting with PCC (mild):
ROH –> RCHO

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25
Q

Alcohol: Oxidation - 2° alcohol to ketone

A

Reagent: H2CrO4
2° alcohol –> ketone
No further oxidation

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26
Q

Forming an alkyl halide from an alcohol involves formation of an _______ species

A

Oxonium

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27
Q

Forming an ether from an alcohol involves formation of an _______ species

A

Alkoxide

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28
Q

Forming an alkene from an alcohol involves formation of an _______ species

A

Oxonium

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29
Q

What is the chemistry of aldehydes and ketones governed by

A

Polarised C=O bond

Presence of lone pairs on C=O oxygen

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30
Q

Aldehydes and ketones - shape

A

C of C=O is sp2 hybridised (flat)

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31
Q

Aldehydes and ketones - oxidation

A

Aldehydes can be oxidised to c. acids in presence of a strong oxidant (H2CrO4)
Ketones can’t be oxidised as there’s no H on the C=O C to remove

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32
Q

Aldehydes and ketones - reactions

A

Nucleophilic addition reaction
For strong Nu, acid must be added after the Nu
For weak Nu, acid must be added with the Nu

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33
Q

Aldehydes and ketones - nucleophilic attack rates

A

Nucleophilic attack is the RDS, and depends on how +ve the sp2 C is; more +ve –> faster reaction

Fastest —————> Slowest
Methanal –> Aldehyde –> Ketone

Trend due to both electronic and steric effects

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34
Q

Aldehydes and ketones - addition of oxygen nucleophiles

A 
1 equivalent --> 1 OH and 1 OR group bonded to C; known as hemiacetal - nucleophilic addition
2 equivalents (excess) --> 2 OR groups bonded to C; known as acetal - substitution
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35
Q

Aldehydes and ketones - forming imines

A

Ammonia or primary amines react with an aldehyde or ketone via addition followed by elimination (of water) to yield an imine
N is a better nucleophile than O so reaction doesn’t require addition of acid catalyst
Imines formed generally unstable but common intermediates

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36
Q

Imine, oxime and hydrazone compounds

A 
Imine:
G = -R, reagent = NH2R (amine)
Oxime:
G = -OH, reagent = NH2OH (hydroxyl amine)
Hydrazone:
G = -NH2, reagent = NH2NH2 (hydrazine)
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37
Q

Carbohydrates - classifications

A

Complex and simple

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38
Q

Complex carbohydrates

A

Consist of two or more simple sugars that are joined together
Hydrolysis of complex carbohydrates breaks them down into the constituent monosaccharide units

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39
Q

Monosaccharides

A

Simple sugars
Consist of a single carbon chain (usually 3-6 Cs long) with one carbonyl group (aldehyde or ketone) with hydroxy groups attached to remaining carbons

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40
Q

Disaccharides and polysaccharides

A

Complex sugars

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41
Q

Monosaccharide - classifications

A

Aldose (contains an aldehyde)

Ketose (contains a ketone)

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42
Q

Enantiomers - multiple stereocentres

A

For a compound with multiple stereocentres, all stereocentres must be reversed to generate the enantiomer
Reversing some but not all in the molecule gives a diastereomer

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43
Q

Relationship between no of stereocentres, stereoisomers and pairs of enantiomers

A

No of stereoisomers = 2^n (where n is no of stereocentres)

No of pairs of enantiomers = 1/2 the no of stereoisomers

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44
Q

D / L-sugars - notation is determined by…

A

The stereochemistry of the centre furthest from the C=O group

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45
Q

D / L-sugars

A

D sugar: stereocentre is R

L sugar: stereocentre is S

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46
Q

Sugars - cyclic hemiacetal

A

One of the alcohol groups can react with the aldehyde or ketone to form a cyclic hemiacetal

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47
Q

Sugars - cyclic hemiacetal formation; size and stability

A

Only 5 and 6-membered cyclic hemiacetals form easily
Size of ring depends on relative stabilities of possibilities
Many carbohydrates exist in an equilibrium between open-chain and cyclic forms

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48
Q

Sugars: Anomers - stereocentres

A

At C-1 in the cyclic form, a new stereocentre is formed

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49
Q

The two hemiacetal forms of a sugar are _________

A

Diastereomers

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50
Q

Anomers

A

Diastereomers that differ in configuration at only one asymmetric carbon

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51
Q

Anomers - classifications

A

α-anomer: when the C1 OH group and C5 CH2OH are trans
β-anomer: when the C1 OH group and C5 CH2OH are cis
System is in equilibrium, so amount of each form depends on relative stability of α and β-anomers - each anomer has 2 potential chair conformers –> total of 4 chair structures to be compared

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52
Q

Anomers - optical rotation

A

α:β ratio is 36:64
When a sample of either pure anomer is dissolved in water the optical rotation slowly changes to +53°
Mutorotation

53
Q

Mutorotation

A

Spontaneous change in optical rotation observed when a pure anomer of a sugar is dissolved in water and equilibrates to an equilibrium mixture of anomers

54
Q

Monosaccharides - ester and ether formation

A

OH groups present in carbohydrates (including anomeric one) can be converted to esters and ethers
H of alcohols replaced by CH3 (ether), or by CH3C=O (ester)

55
Q

Glycoside

A

Acetyl of a sugar is called a glycoside
Stable to water
Not in equilibrium with an open chain form
Don’t show mutorotation

56
Q

Monosaccharides: Forming ester - reagent

A

(CH3CO)2O

57
Q

Monosaccharide: Forming ether - reagent

A

CH3I / Ag2O (mild reagents)

58
Q

Hemiacetal and glycoside - reagents

A

Hemiacetal –> glycoside: CH3OH/H+

Glycoside –> hemiacetal: H3O/H+

59
Q

Disaccharide formation

A

When acetal is formed with OH of a second sugar acting as an alcohol, a disaccharide forms
Glycoside bonds can form between the anomeric C on one sugar and any of the hydroxyl groups on other sugars

60
Q

Carboxylic acids - acidity

A

Moderately weak acids

Ability to delocalise -ve charge in carboxylate anions –> more stable than alkoxides

61
Q

Overall acidity of organic compounds containing an -OH group

A

Carboxylic acid > phenol > alcohol

62
Q

Carboxylic acids - acidity (pKa) correlates with…

A

The electron donating or withdrawing effect of substituents
Groups either stabilise (withdrawing groups) or destabilise (donating groups) the carboxylate ion formed upon deprotonation
Increased stability = increased acidity

63
Q

Carboxylic acids - EDG and EWG

A

EDG decrease acid strength (increase pKa)

EWG increase acid strength (decrease pKa)

64
Q

Alkyl halide to carboxylic acid - Grignard addition

A

RX —Mg and dry ether—> R-MgX

R-MgX + CO2 –> R-CO(OMgX) —H3O+—> R-CO(OH)

65
Q

Alkyl halide to carboxylic acid - nitrile

A

Nucleophilic substitution
RBr —(-)CN—> RCN —H3O+—> R-COOH
Where addition of H3O+ is hydrolysis
Only works for alkyl R groups

66
Q

Carboxylic acids: Nucleophilic acyl substitution involves…

A

Addition followed by elimination (two steps)

Slow step is addition of nucleophile

67
Q

Carboxylic acids: Reactivity order

A

Fastest to slowest:

Acyl chloride > acid anhydride > ester > amide > carboxylic acid

68
Q

Acid anhydride

A

R-CO(OCOR)

69
Q

Nucleophilic acyl substitution: Slow step

A

First step is slow step, so leaving group ability of Y in second step (fast) can’t affect relative rates of nucleophilic acyl substitution
Instead, rate of nucleophilic attack at carbonyl C in first step varies with Y, i.e. size of 𝛿+ charge on C=O (which is also dependent on Y)

70
Q

Nucleophilic acyl substitution: If group Y is electron-withdrawing…

A

e.g. Y = Cl
The polarisation of the carbonyl group will be affected; the C becoming more positive
Therefore reacts relatively rapidly with a nucleophile in RDS

71
Q

Nucleophilic acyl substitution: If group Y is electron-donating…

A

e.g. Y = OR or NR2
It will make the carbonyl C less positive
Therefore reacts relatively slowly with a nucleophile in RDS

72
Q

Anhydride - reaction rate

A

Lies between acid chloride and ester, because while there is the possibility of donation from the O, it results in an unfavourable resonance hybrid (adjacent +ve charges)

73
Q

Amides - reaction rate

A

Least reactive
Donation from lone pair on nitrogen is dominant resulting in a carbonyl group with much less 𝛿+
Lone pairs on N are more readily donated than on O

74
Q

How are acid chlorides prepared

A

By reaction of a carboxylic acid and SOCl2
HCl and SO2 (g) are formed as bi-products in reaction
Reaction is non-reversible

75
Q

Anhydride general structure

A

R-C-O-C-R1
|| ||
O O

76
Q

Formation of carboxylic anhydrides

A
  1. Reacting COOH with a dehydrating agent (e.g. P2O5) –> results in only symmetrical anhydrides
  2. Reacting acid chloride with COOH –> results in both symmetrical and asymmetrical anhydrides
77
Q

Acyl chloride / anhydride to amide reaction

A

RCOCl —R1-NH2—> RCO-NHR1 + HCl (strong and reactive)
Nucleophilic acyl substitution

Anhydride uses same reagents, but instead of giving HCl as bi-product, it gives COOH as bi-product; less reactive than HCl

78
Q

Acyl chloride / anhydride to ester reaction

A

RCOCl —R1-OH—> RCO-OR1 + HCl (strong and reactive)
Nucleophilic acyl substitution

Anhydride uses same reagents, but instead of giving HCl as bi-product, it gives COOH as bi-product; less reactive than HCl

79
Q

Acyl chloride to anhydride reaction

A

RCOCl —R1COOH—> RCO-OCOR1 + HCl (strong and reactive

Nucleophilic acyl substitution

80
Q

Acyl chloride / anhydride to carboxylic acid reaction

A

RCOCl —H2O—> RCO-OH + HCl (strong and reactive)
Nucleophilic acyl substitution

Anhydride uses same reagents, but instead of giving HCl as bi-product, it gives COOH as bi-product; less reactive than HCl

81
Q

Acyl chloride - Grignard reagent

A

Yields 3° alcohol
Reagent: 1. 2R1-MgX, 2. H3O+
Nucleophilic acyl substitution (forms ketone), followed by nucleophilic addition (forms 3° alcohol)

82
Q

Acyl halide + alcohol –>

A

Ester + HCl

83
Q

Carboxylic acid + alcohol –>

A

Ester + H2O

Requires large excess of alcohol (either methanol or ethanol)

84
Q

Hydrolysis of esters

A

RCOOR1 —H2O/H3O+—> RCOOH + R1-OH (bi-product)
RCOOR1 —H2O/OH(-)–> RCOO- + R1-OH (bi-product)
Nucleophilic acyl substitution

85
Q

Ester reaction with amine

A

RCOOR1 —R2-NH2—> RCONHR1 + R2OH

Nucleophilic acyl substitution

86
Q

Reduction of esters

A

Nucleophilic acyl substitution followed by nucleophilic addition
RCOOR1 —1. LiAlH4, 2. H3O+—> RCH2OH + R1OH

87
Q

Ester reaction with Grignard reagent

A

RCOOR1 —1. 2R2MgX, 2. H3O+—> 3° alcohol

Nucleophilic acyl substitution followed by nucleophilic addition

88
Q

Base-promoted hydrolysis of esters (saponification)

A

Strong nucleophile OH- used; no catalyst required

Final carboxylic acid is in its conjugate base form (deprotonated)

89
Q

Acid-catalysed hydrolysis of esters

A

Weak nucleophile H2O used; acid catalyst required
Final carboxylic acid is in its conjugate acid form (protonated)
4 reactive intermediates

90
Q

Formation of 1°, 2° and 3° amides

A

1° amide: acid chloride (or acid anhydride) + ammonia
2° amide: acid chloride (or acid anhydride) + RNH2
3° amide: acid chloride (or acid anhydride) + R2NH

91
Q

Hydrolysis of amide

A

Much less reactive towards nucleophilic acyl substitution, so hydrolysis requires strong aqueous acid or base
e.g. 70% aq. H2SO4 + heat, then OH- (in second step) to deprotonate the NH3+

92
Q

Amide - acidity/basicity

A

Neutral –> very stable
Absence of basicity and low reactivity towards nucleophiles are due to resonance interaction, effectively decreasing availability of lone pair of electrons in nitrogen

93
Q

Amine - N

A

Tetrahedral (sp3 hybrisdised)

Classified as 1°, 2° or 3° for 1, 2, or 3 alkyl or aryl groups directly bonded to N

94
Q

Quaternary ammonium salts

A

Compounds with 4 groups attached to N

N has a positive charge

95
Q

Aliphatic amines

A

N is directly bonded to an sp3 carbon

96
Q

Aromatic amines

A

N is directly bonded to an sp2 carbon of an aromatic ring

97
Q

Amine - naming

A

Where amine is the principle functional group, the suffix amine is used
Where amine functional group is considered a substituent, the prefix amino is used

Prefix N- is used to indicate a group is directly bonded to the N and not a branch on the C backbone

98
Q

Amino acids

A

Bi-functional compounds containing both an amine and a carboxylic acid
α-amino acids: amine group is found on adjacent C (α-carbon) to the carboxylic acid

99
Q

α-carbon of amino acids

A

With exception of glycine (R=H), the α-carbon of an amino acid is a stereogenic centre –> 2 enantiomeric forms possible

100
Q

Naming amino acids

A

Uses L/D rather than S/R

101
Q

Amine - basicity

A

Lone pair of electrons on N can act as a base or as a nucleophile
Exception of quaternary amines

102
Q

Amine - pKa

A

The higher the pKa for the conjugate acid (ammonium salt), the more basic the amine
For simple alkylamines, pKa ≈ 10-11 (in aqueous solution)

103
Q

Amine - pKa trends

A

Least basic —–> most basic
NH3 < CH3NH2 < (CH3)2NH
Inductive effects of alkyl/methyl groups pushes its electrons onto the N –> increased electron density –> increased basicity / pKa

(CH3)3N lies between NH3 and CH2NH2
Steric interaction due to crowding –> decreased basicity / pKa

104
Q

Arylamines (aromatic amines) vs alkylamines

A

In aqueous solution, simple arylamines are much weaker bases than simple alkylamines
Due to delocalisation of lone pair of electrons on N into aromatic ring, making them less available to act as a base

105
Q

Aromatic amines - EWG and EDG

A

EWG: decrease basicity / pKa
EDG: increase basicity / pKa

106
Q

Amine - substitution (SN) of alkyl halide with NH3, RNH2 or R2NH

A

R-X + NH3 –> R-NH3+ –> R-NH2
Here, the product is more basic/nucleophilic, so continues to react with other alkyl halides
–> R-NH-R1 –> (R)3-N –> (R)4-N+Br-

Usually results in mixtures due to product being more reactive

107
Q

Amine and aryl halides - nucleophilic substitution

A

Aryl halides (Ar) don’t undergo nucleophilic substitution to form an amine

108
Q

Best way to make Ar-NH2

A

Reduce Ar-NO2

Ar-NO2 —1. Fe/H3O+, 2. OH(-)—> Ar-NH2 —CH3Br—> Ar-NHCH3

109
Q

Reduction to form an amine

A

Nitrile, 1° amide, imine and oxime: undergo reduction with 1. LiAlH4, 2. H3O+ to form RCH2-NH2 (1° amine)

2° amide and N-substituted imine: undergo reduction with 1. LiAlH4, 2. H3O+ to form RCH2-NHR1 (2° amine)

3° amide: undergo reduction with 1. LiAlH4, 2. H3O+ to form RCH2-NR1R2 (3° amine)

110
Q

-CN to -NH2

A

Reduction

1. LiAlH4, 2. H3O+

111
Q

Amine reaction with acyl chloride

A

Acylation
1° or 2° amine reaction forms amide + HCl
3° amine doesn’t react with acyl chloride - no H on N that can be substituted

112
Q

Amino acids - amphoteric property

A

Can act as either acids or bases

113
Q

Amino acids - acid solution

A

Overall charge is 1+

NH3+ and COOH group

114
Q

Amino acids - neutral solution

A

Molecule exists as a zwitterion - neutral charge
NH3+ and COO- group
Fully soluble in water

115
Q

Amino acids - basic solution

A

Overall charge is 1-

NH2 and COO- group

116
Q

Amino acids can link together…

A

Into long chains by forming amide bonds between the NH2 group of one amino acid and the COOH group of another

117
Q

Dipeptide

A

2 amino acids combine to form a dipeptide

Forms CONH bond

118
Q

Amino acids - naming convention

A

N-terminal amino acid (free NH2) to the left
C-terminal amino acid (free COOH) to the right
e.g. Gly-Ala: N terminal is at Gly, C terminal is at Ala

119
Q

Amide bond formation - complexity

A

If you mixed 2 amino acids (e.g. Gly-Ala), would get a mixture of dipeptides (e.g. Gly-Ala, Ala-Gly, Gly-Gly, Ala-Ala)
If side chain contains a reactive functional group, then even more combinations are possible

120
Q

Peptides vs proteins

A

Chains < 50 amino acids = peptides

Chains > 50 amino acids = proteins

121
Q

Amide bond - shape

A

Planar, with N-H oriented 180 degrees to C=O

122
Q

Structural organisation of proteins

A

Primary: amino acid sequence in peptide chain
Secondary: H-bonding alters local peptide geometry producing coils
Tertiary: disulphide bonds alter entire protein shape
Quaternary: diff proteins aggregate to form new structures

123
Q

Radical (free radical)

A

An atom, molecule, or ion that has one or more unpaired valence electrons
Highly reactive towards other substances

124
Q

How can radicals be generated

A

Homolytic bond cleavage - one electron from the bond ends up on each of the atoms which were formerly bonded

125
Q

Basic steps in radical reactions

A

Initiation: Homolytic bond cleavage of a weak bond to generate 2 radicals. Usually facilitated by light (hv) or heat
Propagation: A free radical reacts with a molecule with no unpaired electrons to generate a new radical (and new covalent bond). No net change in no of radical species present
Termination: Eventually, a radical may combine with a second radical, generating a species with no unpaired electrons

126
Q

Radical reactions - when does propagation end

A

Propagation is a repeating cycle, and will keep going until all the starting material is consumed, or termination occurs

127
Q

Conc of radical species

A

In most radical reactions, conc of radical species are low –> radicals more likely to interact with a non-radical (propagation) than with a second radical (termination)

128
Q

Radical stability

A

The more stable a radical is, the more likely it will survive long enough to encounter a second radical
Thus, stable radicals are more likely to react via termination than unstable radicals

129
Q

What is a factor that increases radical stability

A

Delocalisation (ability to form resonance hybrids)

CHEM 110 (6 decks)

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