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Med chem > med chem 14-26 > Flashcards

med chem 14-26 Flashcards

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1
Q

general structure of carboxylic acids

A

RCOOH contains the COOH (carboxyl group)

C is linked to 3 different atoms

geometry = trigonal planer bond angel 120

in latic acid and citric acid

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2
Q

saturated fatty acids

A

saturated with H

no doubble bonds

rotatable

linear chain

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3
Q

hydrogen bonding in carboxylic acids

A

due to hydrogen bond formation carboxylic acids ahve high boiling points

are water soluble due to H bond

exist as H bonded dimers in liquid state

can usually form 2 H bonds

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4
Q

unsaturated fatty acids

A

at least one doubble bond usually cis configuration

C=C closeest to methyl end

W followed by nukmber of C

veg oil

liquid at room temp

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5
Q

polyunsaturated fatty acids

A

•Double bonds will always be separated by (at least) one methylene group (-CH2-)

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6
Q

prostaglandins

A

•Biosynthesis starts with phospholipids in membrane

Phospholipase A2 frees arachidonic acid (•20 carbon polyunsaturated fatty acid) from membrane

•Arachidonic acid is converted to PGH2 from which other prostaglandins are synthesised

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7
Q

carboxylic acid reactions

A

carboxylic acids react with base to produce salts and water

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8
Q

dissociation (ionization) of carboxylic acids

A

loss of h resuting in a - charge on O

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9
Q

Ka and PKa

A

ka is the acid ionization / dissociation constant

Ka= products / reactants

the larger the KA value the stronger the acid

PKa= log 1/ KA (-log ka)

Strong acids (large Ka) have low pKa values;

Weak acids (low Ka) have high pKa values

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10
Q

Why are carboxylic acids much more acidic than

alcohols, even though both contain –OH groups ?

A

carboxylate conjugate base is stabilised by

resonance, the alkoxide conjugate base is not.

Hence the carboxylate conjugate base is formed more

easily i.e. the carboxylic acid is a stronger acid.

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11
Q

how are carboxylic anions stabalised

A

Stabilised by Resonance

because the negative charge is spread over the two oxygens.

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12
Q

carboxylic acid Substituent Effects on Acidity

A

In RCOOH, substituent R influences the acidity of the -COOH group.

electron withdrawing group will reduce the negative charge on COOΘ and make the conjugate base more stable: more easily formed i.e. carboxylic acid is a stronger acid.

eg: CL,F, nitro groups

electron donating group destabilises the conjugate base: carboxylic acid is a weaker acid.

eg methyl groups

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13
Q

synthesis of carboxylic acids

A
  1. Oxidation of primary alcohols or aldehydes
  2. Reaction of Grignard reagent with CO2
  3. Oxidation of an alkylbenzene with KMnO4 gives a benzoic acid
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14
Q

lipids

A

Natural materials that are mostly insoluble in water

Soluble in organic solvents:

needed for:

nTransport of Vitamins A, D, E and K in the body

nProduction of hormones

nFormation of healthy skin

nProtection of organs

nSource of energy

Formation of cell membranes

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15
Q

esters

A

General formula: R1COOR2

are carboxylic acid derivatives

produced by reaction (esterification) of a carboxylic acid with an alcohol

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16
Q

triglycerides

A

animal and veg fats

are esters

formed from esterfication of fatty acids (acid) with glycerol (alchol)

can be saturated and unsaturated fatty acids

differences in physical properties are due to nature of fatty acid chain

saturated fatty acids have extensive intermolecular forces ( High MP)

unsaturated fatty acids do not have these intermolecular forces due to the doubble bonds

= increased distance = molecules less associated = lower MP

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17
Q

Hydrogenation of Unsaturates

A

Used to harden vegetable oil producing margarine

Reduces the ratio of unsaturated fats

Reduction of an alkene to an alkan

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18
Q

Synthesis of Esters

A

by Fischer Esterification of a Carboxylic Acid.

carboxylic acid reacts with alchol to produce ester and H2O

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19
Q

Application of Le Chatelier’s Principle to Improve Yield of Ester

A

Le Chateliers principle states that any change in a system at equilibrium results in a shift of the equilibrium in the direction which minimises the change

Esterification reactions are equilibria.

To get a good yield of ester, it must be removed as it is formed or an excess of one of the reactants must be used.

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20
Q

saponification ( base promoted hydrolysis)

A

it is used to convert fats (esters) to soaps (sodium salts of fatty acids).

Step1/3. Rate Determining Step – nucleophilic attack by OHΘ on ester carbonyl group

Step2/3. Tetrahedral intermediate decomposes (fast).

Step 3/3. Proton transfer to give products (fast).

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21
Q

hyperlipidemia

A

condition associated with elevation of different forms of lipids in the bloodstream

most important risk factor for atherosclerosis which is a major cause of cardiovascular disease

Arteriosclerosis is the leading cause of death among men and women worldwide

increased risk with diets high in saturated fats and trans fats:

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22
Q

treatment of hyperlipidemea

A

Dietary treatment of hyperlipidemia

Drug treatment of hyperlipidemia (eg. statins)

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23
Q

w-3 fatty acids

A

present in fish oil

can reducue risk of atherosclerosis and heart disease

inhibit platelet function which contributes to blood clots that can cause heart attacks

eg linolenic acid

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24
Q

Phospholipids

A

Upon hydrolysis phospholipids will yield:

¨(2) Fatty Acids

¨An alcohol (glycerol)

¨One additional compound (phosphate)

major lipid component of cell membrane

orientate to exclude water from the lipophilic fatty acid tails

nhe structure of phospholipids gives them good membrane forming properties

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25
Q
A
26
Q

non glycerides

A

prostagglandins = PGE2 and PGD2 and sterioids

27
Q

steroids

A

Contains four rings 3 cyclohexanes and 1 cyclopentane(smaller)

Variations occur in the substituents at particular sites giving rise to different compounds

28
Q

cholesterole

A

Component of all cell membranes

¨Synthetic precursor of the steroid hormones

¨Precursor of the bile acids and salts

Plasma membranes can have around one cholesterol per phospholipid

They immobilize the first few hydrocarbon groups of the phospholipid molecules. This makes the lipid bilayer less deformable and decreases its permeability to small water-soluble molecules.

29
Q

Atherosclerosis

A

hardening and/or thickening on the major arteries

risk factors: High fat diet, smoking, diabetes and high blood pressure

Deposition of Cholesterol from LDL on the walls of arteries

Gradual build up of fat and other deposits such as calcium to form plaque

Plaque restricts flow of blood through arteries

30
Q

cholesterole transport

A

insoluble in water so In the blood stream it is transported in the form of complex lipids

LDL – Low Density Lipoprotein

(bad cholesterol)

HDL – High Density Lipoprotein

(good cholesterol)

31
Q

Complex lipids

A

combination of lipids and proteins produce soluble particles

32
Q

apolipoproteins in LDL and HDL

A

apolipoprotein A (ApoA) in HDL

apolipoprotein B (ApoB) in LDL

33
Q

Lipoproteins

A

Complexes of:

Specific carrier protein (apolipoprotein)

Phospholipids

Triglycerides

Cholesterol

Cholesteryl esters

34
Q

Low density Lipoproteins

A

very rich in cholesterol ~45% & cholesteryl esters

only 23% protein

35
Q

High density Lipoproteins

A

little cholesterole ~ 17%

mostly protein

36
Q

Carboxylic acid derivatives

A

Acid chlorides, anhydrides, acid halide, ester, amide

z=X. X= F,Cl,Br,I = acid halide

Z= -Cl = acid chloride

Z= -OR= ester

Z= -NH2, -NHR, -NHR2 = amide

Z= -0(CO)-R = acid anhydride

37
Q

Reactivity of carboxylic acid derivatives

A

O is more electronegative than carbon

Z more electronegative than carbon

undergoes reaction with nucleophiles

38
Q

nucleophilic substitution reaction of carboxylic acid derivatives how does it differ from reactions of aldehydes/ketones

A

substitution in 2 steps with 1 tetrahedral intermediate

has a leaving group where carbonyl campounds (Aldehydes/Ketones) do not

occurs if :

39
Q

carboxylic acid derivatives leaving group ability and nucleophilicity

A

Reaction occurs if Y is a better leaving group than Nu

40
Q

reactions of acid chlorides

A

hydrolysis product = carboxylic acid + HCl

alcoholysis product = ester + HCl

aminolysis product = amide + HCl

41
Q

Acid Anhydrides

A

symmetrical acid anhydrides : anhydrides formed by the addition of two molecules of carboxylic acid with elimination of water

and unsymetrical by different reaction

42
Q

Reactions of Acetic Anhydride

A

reaction with H2O = cartboxylic acid (RCOOH) + Acetic acid (CH3COOH)

reaction with alchols = ester (RCOOR) + Acetic acid (CH3COOH)

reaction with amines = amide ( RCONH2) + Acetic acid (CH3COOH)

43
Q

Synthesis of Aspirin

A

by reacting salicylic acid with acetic anhydride in the presence of H+ catalyst at 60oC.

produces asprin and ethanoic acid (acetic acid)

Salicylic acid has a carboxylic acid group and a hydroxyl group. So the carboxylic acid group can also form an ester by reaction with an alcohol ( esterfication)

44
Q

Hydrolysis of Aspirin

A

can be hydrolysed in basic or acidic conditions.

Acidic solution (reverse reaction of Fischer esterification)

45
Q

amides

A

Derivative of carboxylic acids

46
Q

distinguish between primary secondary and tertiary amides

A

Primary and secondary are H-bond donors and acceptors)

primary can from up to 3 Hydrogen bonds

secondary can from 2 Hydrogen bonds

47
Q

Properties of Amides

A
  1. Least reactive of the carboxylic derivatives
  2. Geometry around C and N trigonal planar and N is very weakly basic although it has an apparent lone pair of electrons. Also carbon to nitrogen bond is shorter than expected for a single bond.

this is due to ressonance

Lone pair on N is not a free lone pair.

Therefore amides are only very weakly basic.

48
Q

Electrophilicity of carbonyl carbon in amides (carboxylic acid derivatives)

A

reduced electrophilicity of carbonyl’s carbon.

nitrogen decreases electrophilicity by resonance (lone pair) electron donation.

49
Q

Amide Group Geometry

A

Geometry around C and N of peptide group is planar because of resonance

50
Q

Amide / Peptide Bond

A

Peptides (and proteins): amino acids linked together by amide bonds

In peptides, amide bonds are also called peptide bonds

51
Q

Peptide group properties

A

bond is unreactive toward nucleophiles such as water: important factor contributing to the stability of proteins (and peptides) in water.

N is weakl;y basic

C has reduced electrophilicity

Trans conformation for vast majority of peptide bonds

52
Q

synthesis of amides from acid chlorides

A
53
Q

Synthesis of amides from acid anhydrides

A
54
Q

synthesis of paracetamol

A

Paracetamol is a secondary amide

discovered in 1887

Synthesised by reaction of p-hydroxyaniline and acetic anhydride

55
Q

Peptide bond formation

A

formed by reaction of amines with carboxylic acid derivatives

56
Q

General Enzyme Inhibition for Therapeutic Effect

A

To inhibit an enzyme from functioning, one approach is to use a drug which binds irreversibly to the active site and blocks it permanently.

These types of drugs typically react with an amino acid at the active site of the enzyme to form a covalent bond.

eg serine has a reactive OH group is commonly present in enzyme active sites.

57
Q

Aspirin

A

Mode of action:

Inhibits an enzyme called prostaglandin-H2-synthase (PGH2) or cyclooxygenase (COX).

This enzyme converts arachidonic acid to prostaglandins and thromboxanes.

Prostaglandins are hormones which in very low concentrations in the body control production of pain, fever and inflammatory responses

Inhibition of the formation of these relieves symptoms of pain, fever etc.

Reacts with a serine residue in the active site of this enzyme

58
Q

penicillin

A

: b-lactam antibiotics

Mode of action:

Inhibits an enzyme called Glycopeptide transpeptidase.

Reacts with a serine residue in the active site of this enzyme

59
Q

Amines

A

Organic relatives of NH3, obtained by replacing one, two or

three H atoms by organic groups.

Boiling point of amines are higher than their

alkane counterparts due to intermolecular hydrogen bonding.

Because of the lone pair of electrons on

the N: amines are basic (and are nucleophiles).

Nucleophilicity because of the lone pair of electrons on the N.

60
Q

Order of Basicity of Amines

A

Electron donating groups increase basicity of amines - push electron density towards N:

making it easier to accept a proton and therefore a better base.

Electron withdrawing groups decrease

basicity of amines - pull electron density away from N: making it less easy to accept a proton

and therefore a poorer base.

61
Q

Nucleophilic substitution reactions with amines

A

Med chem (2 decks)

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