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CHEM1603 CH > Section F > Flashcards

Section F Flashcards

1
Q

What are the 6 fundamental chemical reaction types?

A

Electrophilic Addition, elimination, nucleophilic substitution, oxidation, nucleophilic carbonyl addition, nucleophilic acyl substitution

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2
Q

What chemical reaction occurs with alkenes (C=C)?

A

Electrophilic Addition

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3
Q

What chemical reactions occur with halides (F, Br, Cl)?

A

Nucleophilic substitution, elimination

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4
Q

What chemical reaction occur with alcohols (O-H)?

A

Nucleophilic substitution, elimination, oxidation

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5
Q

What chemical reaction occurs with ketones (C=O)?

A

Nucleophilic carbonyl addition

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6
Q

What chemical reaction occurs with aldehydes (COH)?

A

Oxidation, nucleophilic carbonyl addition

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7
Q

What chemical reaction occurs with carboxylic acids, acetals, esters and amides?

A

Nucleophilic acyl substitution

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8
Q

What reaction would we use to convert an alkene into an alkyl halide?

A

Electrophilic Addition

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9
Q

What reaction would we use to covert an alkyl halide into an alkene?

A

Elimination

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10
Q

What reaction would we use to convert an alkyl halide into an alcohol?

A

Nucleophilic substitution

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11
Q

What reaction would we use to convert an alcohol into a aldehyde/ketone?

A

Oxidation

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12
Q

What reaction would we use to convert an aldehyde/ketone into a hemiacetal/acetal/hemiketal/ketal?

A

Nucleophilic carbonyl addition

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13
Q

What reaction would we use to convert an aldehyde into a carboxylic acid?

A

Oxidation

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14
Q

What reaction would we use to convert a carboxylic acid into an ester/acid halide/amide?

A

Nucleophilic acyl substitution

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15
Q

What is important about nucleophilic substitution reactions?

A

They are reversible, same reaction can be used in either direction

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16
Q

Define electronegativity

A

The power of an atom in a molecule to attract electrons toward itself - results in a polarised bond with delta +ve and delta -ve partial charges

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17
Q

Define an electrophile

A

An electron loving molecule which has a +ve charge and is attracted to electron rich centres (seeks electrons)

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18
Q

What direction would a curved arrow point between an electrophile and nucleophile?

A

Tail of arrow would begin at nucleophile and end at electrophile (head)

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19
Q

When adding HCl to an alkene, what reaction occurs, what is the intermediate and what is the product?

A

Electrophilic Addition, Carbenium/Carbocation, alkyl halide (H and Cl bound to diff. carbons)

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20
Q

When adding H2O to an alkene, what is the process and product?

A

Electrophilic addition, electron density from C=C bond attracted to H+ from H2O, creates +ve charge on other C which H2O then attracted to, O of H2O is +ve so loses an H+, alcohol formed

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21
Q

What is the rule of Markovnikov?

A

When an unsymmetric reagent adds to an unsymmetric alkene, the electropositive part of the reagent bonds to the carbon of the double bond that has the greater number of hydrogen atoms attached to it.

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22
Q

What is the most stable carbocation?

A

R3C+, then R2HC+, then RH2C+ then H3C+ (least stable) - electrophilic addition proceeds in a way to involve the most stable carbocation

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23
Q

Define regioselective

A

If a reaction has a preference for 1 of 2+ stereoisomers (regioisomers)

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24
Q

What is cholesterol synthesised from?

A

Squalene

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25
Q

What is elimination the reverse of?

A

Electrophilic Addition

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26
Q

What is the general reaction for a nucleophilic substitution?

A

Nu: + R-L —> R-Nu + L-

27
Q

What properties must nucleophiles and leaving groups have?

A

Nucleophile: electron excess (lone pair, charge), Leaving group: polarised carbon-L bond, stable as anion

28
Q

What is the reaction for the extension of glucose?

A

SN: UDP-Glucose-Uridine + Glycogen (n) —> Uridine + Glycogen (n+1): glucose incorporated into glycogen

29
Q

How many steps are in a bimolecular nucleophilic substitution (SN2)?

A

One step

30
Q

How does the nucleophile attack in SN2?

A

Backside attack, causes umbrella flip

31
Q

What is bound to reactant in transition state of SN2?

A

Both the nucleophile and leaving group are bound to carbon centre in transition state

32
Q

What does the reaction rate depend on in SN2?

A

[Nu] and [Substrate]

33
Q

What type of halide has the fastest reaction in SN2?

A

Primary halide has fastest reaction

34
Q

How many enantiomers are formed in SN2?

A

Only one pure enantiomer is formed as reactions are stereospecific

35
Q

How many steps are in a unimolecular nucleophilic substitution (SN1)?

A

Two steps, bond broken between carbon and leaving group before nucleophile comes in

36
Q

What does the reaction rate depend on in SN1?

A

Only [Substrate]

37
Q

What type of halide has the fastest reaction in SN1?

A

Tertiary Halide has fastest reaction

38
Q

How many enantiomers are formed in SN1?

A

2 enantiomers formed, 50/50 mix of enantiomers -> racemisation

39
Q

What type of nucleophilic substitution reaction has a rate retarded by polar protic solvents?

A

SN2 has a retarded rate whereas SN1 has an increased rate using polar solvents

40
Q

Which type of nucleophilic substitution reaction is not dependent on [Nu]?

A

SN1 (only [Substrate] matters)

41
Q

Which nucleophilic substitution reaction favours a neutral nucleophile?

A

SN1 favours a neutral nucleophile, SN2 favours an anion

42
Q

What is an example of a good polar protic solvent?

A

H20 and EtOH

43
Q

Are negative or neutral ions more nucleophilic?

A

Negative (Anions) more nucleophilic e.g. H2O

44
Q

How does nucleophilicity vary down the periodic table?

A

Atoms become more nucleophilic as you go down the periodic table

45
Q

What is the Geranyl Diphosphate -> Geranoil reaction an example of?

A

SN1 Nucleophillic substitution

46
Q

What is an example of an SN2 reaction?

A

Norepinephrine + S-adenosylmethionine —> Epinephrine + S-adenosylhomocysteine

47
Q

What 2 different types of elimination reactions are there?

A

E1 (two step) and E2 (one step)

48
Q

Can an aldehyde be oxidised to a carboxylic acid?

A

Yes, but Ketones cannot

49
Q

Is a primary alcohol or secondary alcohol more difficult to oxidise?

A

Primary alcohols are more difficult to oxidise, they are oxidised to aldehydes, whereas secondary alcohols are oxidised to ketones

50
Q

What are secondary alcohols oxidised to?

A

Ketones

51
Q

What are 2 oxidising agents & solutions?

A

K2Cr2O7 and H2SO4 (breathaliser), AgNO3 and NH3 (tollens)

52
Q

What is the mechanism for oxidation?

A

Nucleophile attacks proton next to alcohol, electron density moves to form C=O bond OR nucleophile can attack alcoholic proton

53
Q

What is the shape of the intermediate in nucleophilic carbonyl addition?

A

Tetrahedral

54
Q

What type of nucleophile requires activation of the carbonyl group by acid catalysis?

A

Weak nucleophiles, create resonance stabilised carbocation with +ve charge swapping between C and O

55
Q

What are chemist’s reducing agents?

A

LiALH4 and NaBH4 (& H+/H2O)

56
Q

What are nature’s reducing agents?

A

NADH

57
Q

What occurs during reduction of a C=O bond in Nucleophilic carbonyl addition?

A

nucleophile attacks +ve carbon, electron density from double bond moves onto O to make O- which then acts as a nucleophile for nearby hydrogen

58
Q

What chemicals are used to convert a benzene ring with C=O bond to alcohol?

A

LiAlH4 and THF for first step, then H+ and H2O for second step

59
Q

What is a hemiacetal/hemiketal?

A

Derived from an aldehyde/ketone where an alcohol group is added to the carbonyl group - COROH

60
Q

How do you form a hemiacetal?

A

Nucleophilic attack of an alcohol

61
Q

What is Keto-Enol tautomerism?

A

Chemical equilibrium between keto form (ketone/aldehyde) and an enol form (alcohol w/ double bond)

62
Q

What are the 3 steps in the Aldol Condensation?

A

Enolate formation, nucleophilic addition, protonation

63
Q

What are the reactions and products used in the Aldol condensation?

A

Acetaldehyde is reactant and 3-hydroxybutanal is the product, OH- ions used as catalyst

CHEM1603 CH (6 decks)

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