lecture 1 Flashcards

1
Q

Definition of a curly arrow

A

Movement of a pair of electrons

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2
Q

Reduced structure

A
  • carbons omitted
  • hydrogen attached to carbons omitted
  • hydrogens attached to heteroatom stay
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3
Q

What is the definition of resonance

A

Movement of electrons

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4
Q

What is the definition of tautomerism

A

Movement of one or more double bonds and a small atom ( usually H)

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5
Q

what is the definition of conjugation?

A

alternating single and double bonds

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6
Q

What is conformation?

A

bond rotation , no bond breaking

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7
Q

What energy state is more stable, staggered or eclipsed?

A

staggered

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8
Q

What is the Phi angle rotation about?

A

Rotation about the N - C alpha bond

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9
Q

What is the Psi angle rotation about?

A

Rotation about the C alpha - CO bond

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10
Q

What is configuration?

A

Different configurations are obtained by bond breakage

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11
Q

What is the definition of chirality?

A

Chiral objects do not have an internal plane of symmetry

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12
Q

What form (R or S) are amino acids?

A

s

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13
Q

What are enantiomers?

A

non - superimposable , mirro images

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14
Q

What is a prochiral species?

A

has the potential to become chiral

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15
Q

What is an diastereomer?

A

Non superimposable, non mirror image

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16
Q

What is a meso compound?

A
  • Meso object is one that contains chiral parts but overall chiral (as it contains a plane of internal symmetry)
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17
Q

How do you work out the number of stereoisomers in a compound?

A

2^N , where N is the number of chiral centres

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18
Q

where is the cyanohydrin seen in nature?

A
  • millipedes

- reverse the reaction to get poison

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19
Q

What to remember for base catalysed semi-acetal formation?

A

you have to form the nucleophile first

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20
Q

What type of interaction is hydride transfer?

A

Soft - Soft interaction

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21
Q

How can you solve most of the problems with peptide synthesis?

22
Q

Advantages of solid phase synthesis

A

you can purify as you go

23
Q

Disadvantages of solid phase synthesis

A

You have to limit polypeptide length

24
Q

What happens to the water in the DCC reaction?

A

DCC locks up water in the peptide bond formation, driving equilibrium to RHS

25
What molecules do you need for cyanohydrin formation?
NaCN and H30 plus
26
What type of catalysis does acetal formation need? base or acid?
Acid only
27
What are mine formation and acetal formations an example of?
Nucleophilic substitution with loss of carbonyl group's oxygen
28
Why is water a good leaving group?
Because its conjugate acid (H3O) has a low pKa
29
What do you have to do to get from a hemiacetal to an acetal?
Kick the OH out and replace with an RO
30
What is an example of an imine in nature?
In DNA , cytosine
31
Which is more stable =, the enol or the ketone?
The ketone, enols are generally unstable
32
What is an example of a stable enol?
phenol
33
Which catalysis does enol formation have?
both - acid and base
34
What is formed in the aldol reaction?
C-C bond formed
35
What type of catalysis is the aldol reaction?
acid - catalysed
36
What two components are needed in the aldol reaction?
An enol and an aldehyde
37
What are esters reluctant to form?
enrols , but thiol esters are not
38
What is an example of an aldol reaction in nature?
In the citric acid cycle.Converting Acetal CoA and oxaloacetate into citrate
39
What role doe the oxaloacetate play in the aldol reaction?
The aldehyde
40
What role does the acetyl - CoA play in the aldol reaction?
The enol
41
What is The role of aspartic acid In citrate synthase ?
Take an H , is a base
42
What is the role of Histidine in citrate synthase?
Acid and base
43
how do you draw tautomerism?
The double bond arrow allows go the dashed line
44
Where do bulky side group sit in a chair conformation?
On the equatorial bonds
45
Why can something have a lower pka?
more conjugate bases, more stability
46
Why are aldehydes more reactive than ketones?
- Ketones have 2 stabilising effects where as aldehydes only have one which makes them more stable
47
When determine the ionisation state, do you draw the arrow from the pKA or the pH?
Draw it from the pKA
48
What must you remember when drawing chair conformers?
There are two conformers
49
What makes a strong nucleophile?
- Has a negative charge, weakly electronegative and large (polarisability)
50
What do you have to remember with the 90 degree Psi rotations?
You can then see the double bond O