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Environmental Chemistry > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

What is heteroatom oxidation?

A

It’s when a heteroatom and a O bond to each other. The heteroatom get a positive charge and the oxygen get a negative charge.
X+ — O-

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2
Q

In heteroatom oxidation, what heteroatoms are the most important ones?

A

N and S

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3
Q

What is a-hydroxylation?

A

When a H, i a C—H near a heteroatom, gets replaced with a OH-group.

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4
Q

Why is hydroxylamine the most toxic one on page 46?

A

???

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5
Q

What is more toxic: aliphatic amines or aromatic amines?

A

Aromatic amines. Propably because they are unsaturated and have delocalized pi electrons.

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6
Q

Heteroatom oxidation: What is the major path?

A

N-oxidation. Where the aromatic amine reacts with P450 and a OH binds to the NH. This can either become a radical and lead to radical reactions, or it can kickout sulfite and it become a strong electrophile (?).

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7
Q

Heteratom oxidation: What is the minor path?

A

Epoxidation. An aromatic amine reacts with P450 and get epoxidised. The ring with the O continue to reacts and become OH and then react sith peroxidase and form a double bond to the O. It is a electrophile.

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8
Q

Is the leaving ability of a leaving group stronger if it is connected to a heteroatom or carbon? Why?

A

The leaving ability is stronger if it’s connected to a heteroatom because it allows Nu to attack on different positions.

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9
Q

Are weak acids strong or weak leaving groups? And weak bases?

A

Weak acids = bad leaving groups.
Weak bases = good leaving groups.

The best leaving groups want the electrons???

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10
Q

Why is the oxidation of 1-aminonaphthalene into hydroxyamine slower than 2-aminonaphthalene?

A

Because 1-aminonaphtalene have steric hinders.

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11
Q

Is DMSO mostly reduced or oxidized?

A

Its major “end product” has been oxidized while the minor has been reduced.

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12
Q

Draw the oxidation of a primary alcohol, secondary alcohol and acetone.

A

P. 51

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13
Q

When it comes to oxidation of alcohols and aldehydes: how does the concentration of NAD+ and NADPH affect it?

A

Low conc. of NAD+ and high conc. of NADPH: A reduction will take place.
High conc. of NAD+ and high conc. of NADPH: Oxidation is the primary pathway.

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14
Q

In mammals, what concentration levels do we have of NAD+ and NADPH?

A

We have high conc. of NAD+ and low conc. of NADPH —> oxidation is the primary pathway

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15
Q

Can tertiary alchols be oxidized to aldehydes or ketons? If no, how can it be oxidized?

A

No, because it doesn’t have any hydrogen on its carbon.

It can be oxidized in the beta-carbon (phase I) kr conjugation with glucuronic acid (phase II).

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16
Q

What 3 kind of phase I reductions is there?

A
  1. Reduction of ketones and aldehydes
  2. Reduction of oxidized heteroatoms
  3. Reductive dehalogenation
17
Q

What can ketones and aldehydes be reduced to? What favors this?

A

They can be reduced to alcohols.

This is favored by a low conc. of NAD+ and high conc. of NADPH, and low conc. of oxygen (oxidation needs oxygen)!

18
Q

Why are aromatic amines toxic?

A

Because they can form electrophiles and radicals.

19
Q

What is reductive dehalogenation? What halogens?

A

It’s the removal of a halogen and it’s replaced with a H. X = Cl, Br, I.

20
Q

During the metabolism of DDT, what steps are there?

A
  1. Reductive dehalogenation
  2. a-hydroxylation
  3. Get rid of HCl
  4. Hydolysis
    —> major metabolite of DDT is DDA
21
Q

Why is DDT NOT that dangerous to eat?

A

It is very lipophilic and it doesn’t have any polar groups (hydroxy groups, amino groups etc), it doesn’t dissolve very well in our stomach. If it is poorly dissolved, it is poorly absorbed —> most will go right through us.

22
Q

Name the 2 phase I hydrolyses.

A
  1. Hydrolysis of epoxides

2. Hydrolysis of esters and amides

23
Q

Are epoxides dangerous to humans?

A

Epoxides doesn’t have a very big chance of reaching DNA or protein, because our bodies takes care of epoxides very fast and efficient.

24
Q

Why is the smoke from cigarettes and BBQ dangerous?

A

Because the chemical that comes from incomplete combustion is epoxidized, hydrolyzed and epoxidized again. The last epoxidation can’t fit for epoxide hydrolyze which means it can travel through our bodies and go to DNA and react with it —> toxic!
Metabolic activation.

25
Q

Why is hydrolysis of esters and amides good?

A

Because the products are much more soluble in water

26
Q

Which one is faster, the hydrolysis of amides or esters? Why?

A

The hydrolysis of amides is slower than that of esters. This is because the amide bond is resonance stabilised compared to the ester bond.

N—C is stronger in amides than the O—C in esters (?).

27
Q

Name another metabolic pathway of esters and amides.

A

a-hydroxylation. (?)

28
Q

Name the 4 phase II reactions.

A
  1. Conjugation with glutathione (only used for electrophiles)
  2. Conjugation with sulphate (hydroxy-groups can be conjugated with/by these)
  3. Conjugation with glucuronic acid (hydroxy-groups can be conjugated with/by these)
  4. Conjugation with amino acids
29
Q

Why is conjugation with glutathione important? Which part is most important?

A

Glutathione: G-SH
SH: nucleophilic, can react with all electrophiles.
It is our natural body guards for radicals and if conjugates with electrophiles.

30
Q

Draw a picture where glutathione participates in a reaction where there is:

  1. Leaving group
  2. Michael acceptor
  3. Cyclig ether
A

P. 65

31
Q

What happens, from a toxicological perspective, when we loose a lot of body fat quickly?

A

There is a lot of hydrophobic molecules stored in our body fat, if reduce the body fat quickly then these molecules will be realeased in our blood stream which can cause problems.

32
Q

What can you use methylating agents for?

A

To silence parts of the DNA that doesn’t need to be expressed. Some parts of the DNA is methylated which makes it inactive.

33
Q

What is conjugation with sulphate usually used for? Advantage and disadvantage?

A

Primarily for alcohols and phenols.

It is fast but is has a low capacity because the amount of PAPS in our bodies is limited.

34
Q

What happen when phenol and PAPS react?

A

It forms a molecule that i very hydrophilic. It’s ionic at pH 7.

35
Q

What kind of units can be used during conjugation with glucuronic acid?

A

For example: alcohols, phenols, carboxylic acids etc. They only need to be more nucleophilic than electrophilic, then they will react.

36
Q

How is the units excreted after conjugation with glucuronic acid?

A

Via the kidney: M<500

Via the liver: M>500

37
Q

What happen if glucuronic acid is conjugaged to a hetero atom (e.g. N)? What kind of conditions does it need to be? Draw it!

A

It will/can(?) form an active carcinogen. It need to be under weakly acidic conditions (urine).
If there is a hydrolysis under weakly acidic conditions (low pH), the molecyule will be absorbed by the bladder and sulfation leads to metabolic activation —> active carcinogen.

38
Q

What compund is conjugation with amino acids primarily used for?

A

It’s primarly for carboxylic acids. Carboxylic acids can be conjugated by both glucuronic acid and glycine.

Environmental Chemistry (6 decks)

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