WORLD OF MOLECULES

(1)

Development of Complex Curricula for Molecular Bionics and Infobionics Programs within a consortial* framework**

Consortium leader

PETER PAZMANY CATHOLIC UNIVERSITY

Consortium members

SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER

The Project has been realised with the support of the European Union and has been co-financed by the European Social Fund ***

**Molekuláris bionika és Infobionika Szakok tananyagának komplex fejlesztése konzorciumi keretben

***A projekt az Európai Unió támogatásával, az Európai Szociális Alap társfinanszírozásával valósul meg.

PETER PAZMANY CATHOLIC UNIVERSITY SEMMELWEIS

UNIVERSITY

(2)

WORLD OF MOLECULES

Important hints for practices of organic synthesis

(Molekulák világa )

(Fontos gyakorlati tanácsok a szerves kémiai szintézishez)

semmelweis-egyetem.hu

World of Molecules: Hints for practices

Compiled by Péter Mátyus

with contribution by Gábor Krajsovszky

Formatted by Balázs Balogh

(3)

Glassware

– Cracked or damaged glassware should not be used for any work

Heating

– It is forbidden to work in a closed system – boiling-stones, stirring

– Flammable solvent: water bath or oil-bath (The use of free flame is forbidden!)

(4)

– Chemicals in the eye

wash the eye immediately with much water

neutralization with 1% NaHCO₃-solution (in the case of acids) washing with 1% boric acid-solution (in the case of base)

– Chemicals on the skin wipe it with dry towel washing with water

washing with NaHCO₃-solution or 1% boric acid solution – Cuts

blooding, washing, bandage

First aid

(5)

Burning

cold water

sterilized gause

Burning clothes should be extinguished by rolling in a fire blanket or by using the safety shower.

Swallowed chemicals medical help Handling of waste materials

labelled vessels

For special waste materials, there are different vessels (e.g. strong inorganic acids, bases, oxidizing or reducing agents, halogen-containing and halogen-free solvents).

(6)

Laboratory equipments

(7)

Parts of preparation

• Checking literature

• journals or electronic databases

• elaborate an economic pathway

• Planning of the reaction - reagents

- assemble the apparatus of appropriate size - main steps

- measuring the reagents - reaction

- isolation - purification - identification

(8)

• Carrying out a reaction:

- assemble of an apparatus

the system must not be closed clamps and clamp holder

the ground-glass joints

cooling water in the condenser is streaming

- Adding the reagents

- Stirring, heating, cooling, gas outlet

(9)

Stirring:

Magnetic stirring Mechanical stirring

apply proper stirring rate

(10)

Heating:

- Bunsen flame:

for heating baths or liquids with high boiling point ceramic net or bath

boiling stones to avoid overheating - Magnetic stirrer:

water or oil bath Boiling:

heating of a reaction mixture to its boiling point (reflux)

Liebig condenser

rate of dropping back (1 drop/sec)

(11)

Cooling:

- Condensing vapors:

Liebig-, ball-, spiral codenser - Cooling bath

tap-water

ice-water (0^oC)

salt-ice mixture (0-[-20]^oC)

dry organic solvent mixture ([-20]-[-78]^oC)

(12)

• Working up reaction mixtures

Separation and purification of the products.

The reaction mixture contains several components (product, solvent, reagents, educts, side-products).

You should not throw away any rest material before having completed the isolation.

Typical cases:

- The product precipitates: filtration, washing, recrystallisation - The product does not precipitate:

distillation of the solvent, then crystallization (non- volatile product); or: purification by extraction and distillation (volatile product)

(13)

Liquid-liquid Extraction/Washing

Method by which material is selectively transferred from one into the other phase of mixture of two immiscible solvents.

Liquid-liquid extraction K= distribution coefficient

K=C

₁

/C

₂

(C

₁

ill. C

₂

: concentrations of the compound in the

phases

K is characteristic for the material

(14)

Different density

High solubility in the solvent (K value) Organic phase-aqueous phase

The solvent must be volatile Salting out

Changing pH influences K value Design of extraction:

(15)

Separatory funnel

- Control the ground glass joint of stopper and the stopcork

- Place the separatory funnel into the Bunsen ring

- Transfer the phases into the separatory funnel through funnel

- Shaking - Venting!

- Separation

Problems of separation: formation of emulsion. In this case, rotate gently the separatory funnel or add salt

(16)

Drying

Liquids and solutions

removal of traces of water – Drying of a solvent

– Drying of a solution

– anhydrous Na₂SO₄, MgSO₄, K₂CO₃, CaCl₂

Stirring for 10-30 min in order to get clear solution Filtration through fluted filter paper

Evaporation

Removal of greater amount of water: by fractional or azeotropic distillation

If small amount of water is present, molecule sieve can be used for drying (reversible storing of water molecules) Adding a reactive compound (Na metal, P₂O₅, metal hydride):

it reacts with protic solvents, then distillation is needed. Reacts extremely vigorously, extra care is needed!

(17)

Some more important drying agents

Drying agent Hydrate formed Capacity Remark

CaCl₂ CaCl₂·6H₂O medium Fast. Not useful for alcohols, amines, acids.

Na₂SO₄ Na₂SO₄·10H₂O great Cheap. Reacts slowly. Inert.

CaSO₄ CaSO₄·2H₂O small Strong drying effect.

K₂CO₃ K₂CO₃·2H₂O medium For drying esters, ketones, nitriles.

MgSO₄ MgSO₄·7H₂O medium Quick. Inert.

P₂O₅ H₂PO₃/H₃PO₄ medium Strong. Not useful for H-donor or -acceptors.

CaH₂ Ca(OH)₂+ H₂ great Great efficiency. Previous drying is needed. Not useful for alcohols.

Na NaOH + H₂ great

Great efficiency. Previous drying is needed.

Dangerous!

Not useful for chloroform.

CaO Ca(OH)₂ medium Slow, but efficient. Useful for alcohols, amines.

NaOH/KOH solution medium Quick, efficient. Useful for amines.

Molecule sieve adsorption small Quick, efficient. Useful for keeping solvents dry.

(18)

Drying Solid material

To remove water and organic solvent Simply in air

By absorption of vapors in a desiccator

By vacuum in a vacuum oven:

Vacuum desiccator

(19)

Gravitational filtration of a suspension with fluted filter paper

Separation of a solid material from liquid Removal of the charcoal: filtration of the saturated hot solution through fluted paper

Prevention of the crystallization in the funnel:

Use warm funnel

Warm the funnel before the filtration Wet the paper with hot solvent

Crystallization

Cooling slowly (the size of the crystals)

(20)

Filtration

Filtration by reduced pressure (suction filtration)

Separation of a precipitate from the mother liquid Büchner funnel with filter paper

Büchner flask

Steps of suction filtration: filtration, washing with cold solvent in order to remove the mother liquid, drying

Water pump

(21)

Dangerous operation

We heat the liquid to boiling, and after condensation of the vapor, the material is collected in another flask

Types of distillation:

1. Simple distillation: at atmospheric pressure, for liquids boiling below 150^oC, evaporation

2. Vacuum distillation: for liquids boiling above 150^oC and/or being heat- sensitive

3. Fractional distillation: (rectification) for separation of liquid mixtures by using column according to the boiling points of the components, if the difference between the boiling points is less than 25^oC

4. Steam distillation: see later

Distillation

(22)

Simple distillation:

appropriate apparatus, receiver flask for the different fractions mercury ball of the thermometer

cooling water, stirring, heating different fractions

rate: 1 drop/sec

Monitoring temperature, volume of the distillate, distillation temperature of the main fraction are necessary.

(23)

Apparatus for fractional distillation

Difference between the boiling points of the

liquids to be separated is less than 25

^o

C

Distillation column

(24)

Conditions of fractional distillation

♦ The components must not form azeotropic mixture with each other

♦ Perfect drying is needed

♦ Length of the column should be chosen according to the b.p. difference of the components (the smaller the b.p. difference, the longer the column)

Advantages of fractional distillation

♦ The components can be distilled one by one in high % and in high purities

Disadvantages of fractional distillation

♦ There are always intermediate fractions and distillation residue

♦ Cleaning of the main flask after long distillation period might be difficult (the compounds are burned into the flask)

♦ Lot of time and lot of energy is needed, there are other alternatives

♦ More skill is needed to get the main fractions with top qualities World of Molecules: Hints for practices

(25)

Apparatus for vacuum distillation

nitrobenzene

water

pressure in mm temperature o C

(26)

Conditions of vacuum distillation

♦ The compound must not form azeotropic mixture with water

♦ There must not be present any insoluble impurity

♦ Pay attention on using unbroken glassware only

Advantages of vacuum distillation

♦ Lot of time and lot of energy is saved, since much lower bath temperature is used

Disadvantages of vacuum distillation

♦ Getting data on the main fraction is more complicated, temperature- pressure pairs should be read continuously

♦ It is usually not good for separation of liquid components, unless they have b.p. difference of more than 100^oC at atmospheric pressure

♦ Changing the fractions is possible by rotation of the receiver only

♦ There is extremely high danger of explosion

(27)

Evaporation at reduced pressure Rotational vacuum evaporator (ROTA)

It is for the elimination of solvent(s), we want to get the distillation

residue.

Problem: distillation of solvents from a reaction mixture does not characterize the distillation

residue!!!

vacuum

Alternative of vacuum distillation:

(28)

Steam distillation Conditions:

1.) Do not mix (immiscible) with water 2.) Volatile with water

3.) Do not react with water

P = P

_A

+P

_B

(29)

Disadvantages of steam distillation

♦ Lot of energy is needed, and the use of overheated water can be dangerous

♦ Careful adjusting the rate of boiling water and the rate of the distillation of the reaction mixture is needed in order to have 0 net flux (the level of the reaction mixture must remain the same during the whole process)

♦ It might not be a good process if more than one component is volatile

♦ Other organic solvents should not be present

(30)

For purification of solid materials

Base: solubility depends on the temperature Steps:

- Select an appropiate solvent

- Preparation of a hot, saturated solution - Clarification (charcoal)

- Filtration of the hot solution - Cooling – crystallization - Filtration by suction

- Drying

Crystallization

(31)

Aspects of selecting the solvent

- No reaction is allowed with the material

- Good solubility at the boilig point, slight solubility at low temperature

- It should dissolve the impurities at low temperature well, or at high temperature slightly or not at all

(32)

Preparation of the saturated hot solution

Flammable solvent

Round-bottom flask, with termometer Boiling stones (chips) or stirring

Water or oil bath

Adding the necessary amount of the solvent and boiling

(33)

Not flammable solvent (e.g., water):

Erlenmeyer-flask Boiling chips

Ceramic pad Bunsen-flame

Adding the necessary amount of the solvent and boiling

(34)

Clarification

Removing of colored as well as apolar impurities (charcoal) Hot, but not boiling solution + 1-5% charcoal

1-2 minutes boiling

(35)

Control the purity of the sample

The products should be characterized by physical constants which show their purity. For identification and structure determination, various spectroscopic methods are used.

- Determination of melting point - Checking of the boiling point - Refractivity

- Thin-layer chromatography - Spectroscopy (IR, NMR, MS) - Elemental analyses

(36)

Melting point determination

Melting point: temperature at which the solid and the melted form is in equilibrium (melting range)

For identification and characterization of the purity of the sample Thiele apparatus

(37)

Chromatography

It is a separation method based on the selective distribution of the

components of a mixture between the stationary and the mobile phase.

The components of the mixture move by different rate along the stationary phase, the component having stronger interaction with the stationary phase remains behind (retention).

Mobile phase

(38)

Classification

mobile phase stationary phase

Solid Liquid

Gas gas-solid chromatography (Adsorption gaschrom.)

gas-liquid chromatography (Distribution Gaschrom.)

Liquid

liquid-solid chromatography (Adsorption Liquidchrom.) - Thin layer chromatography

- Classic column chromatography

liquid-liquid chromatography

(Distribution Liquidchrom.) Paperchromatography According to the state of the phases

(39)

According to the mechanism of the separation

What kind of interaction does take place in the separation?

Adsorption, distribution, biological affinity, ion exchange, exclusion by size, complex formation, etc.

Adsorption chromatography

interaction: equilibrium between the adsorption to the active surface sites of the stationary phase and the desorption caused by the mobile phase.

Adsorption depends on polar interactions mainly: coordinative interactions, secondary interactions (e.g., hydrogen bridge, dipole-dipole interaction).

Retention is determined by the character, number and spatial arrangement of the polar groups in the molecule.

(40)

According to the polarity of the stationary and mobile phases Normal phase chromatography:

Polar stationary phase – apolar mobile phase

Retention increases by increasing polarity of the molecule.

(Typical stationary phases: silica gel, aluminium oxide, cellulose)

Reverse phase chromatography:

Apolar stationary phase – polar mobile phase

Retention decreases by increasing polarity of the molecule.

(Typical stationary phases: silica gel modified by alkyl silanes) World of Molecules: Hints for practices

(41)

According to the technics used column chromatography:

The stationary phase is placed into a column.

Preparative method

- Classical column chromatography

- Quick (flash) column chromatography

- Liquid chromatography with great efficiency (HPLC) flat orientation chromatography:

Separation takes place in two dimension Mostly analytical method

-Paper chromatography

-Thin layer chromatography

(42)

Technics: - Flat orientation

- Separation happens on a thin (0.5-2 mm) stationary phase fixed on glass or aluminium sheet.

-Mobile phase (eluent) is moved by the capillary effect.

- Chromatogram is developed in a closed container

B front

start

A

R_f= A / B spot of the compound

R : retention factor, its value is between 0 and 1, the ideal range: 0.3-0.8

eluent

top of the container

container

thin layer sheet

Thin layer chromatography

(43)

Stationary phase (adsorbent)

The usual stationary phases of thin layer chromatography:Silica gel,

aluminium oxide, cellulose, polyamide, compound with modified surface, ion exchange resins

Silica gel

Polar – normal phase chromatography

It is prepared by dehydration of silicic acid (H₄SiO₄) with great relative surface (200-1000 m²/g)

Silanol (Si-OH) groups can be found on its surface

Adsorption is influenced by water adsorbed on its surface (decreasing activity)

Standardized sheets are used.

Increasing order of adsorption (on normal phase):

alkanes, alkenes, ethers, alkyl halogenides, aromatic compounds, ketones, aldehydes, esters, alcohols, amides, amines, carboxylic acids

Si O

O O

O Si

Si

Si HO

OH

O Si O HO

HO

O Si O O

(44)

Mobile phase (eluent)

It is usually an organic solvent, or mixture of organic solvents

The elution ability of solvents increases by increasing polarity of the solvents

Increasing elution order:

Petrolether, cyclohexane, toluene, dichloromethane, chloroform, diethyl ether, ethyl acetate, acetone, ethanol, methanol, water, acetic acid

Detection

-by UV lamp (254 nm/366 nm)

-by developing reagent (e.g., iodine, cerium(IV) salts, phosphoric acid) World of Molecules: Hints for practices

(45)

How to carry out thin layer chromatography 1

- Prepare the container: fill with eluent with height of about 5 mm

- Mark position of the samples by a pointless pencil

(keep distance of 10 mm from the bottom of the sheet and between the spots)

- Prepare solution from the compound to-be- examined

- Apply 1 or 2 drops from the sample by capillary to the TLC plate, and dry it

- Place the TLC plate into the closed container saturated by vapors of the eluent.

Close the container, and do not move!

+ +

(46)

How to carry out thin layer chromatography 2 - Pick up the TLC plate from the container,

before the front reaches top of the TLC plate - Mark position of the front line by a pointless

pencil -Dry the TLC plate by hair drier - Mark position of the spots by a pointless

pencil under UV lamp (or develop) - Calculate retention factor

+ +

(47)

Possible uses of TLC:

- checking course of a reaction

- determination number of the components in the (reaction) mixture - checking presence of some components

- modelling column chromatography (choosing eluent) or detection - examination of purity

Limits of TLC:

- mainly qualitative method

- volatile compounds can not be used

- with limited resolution (many eluents must be checked until receiving perfect separation)

(48)

Separation carried out on preparative scale

Stationary phase (most often is silica gel) is filled into vertical column.

The eluent is moved by gravity.

Pour the sample to-be-purified to the top of column (adsorb it to the top layer of the stationary phase) Add more eluent from above

Collect fractions

Check ingredients of the fractions (by TLC)

Unify the proper fractions, and evaporate the solvent(s) Choosing eluent:

model by TLC (R_f: 0.1-0.6 must be) Amount of the stationary phase:

25-100 times of the sample to-be-purified

Classical column chromatography

(49)

Dropping rate of the eluent

Influences efficiency of the separation

Two opposite processes must be taken into account:

If dropping rate is low

- great diffusion – decreases efficiency

- there is time for making equilibrium (adsorption- desorption) – increases efficiency

If dropping rate is fast - diffusion is negligible

- there is no time for making equilibrium

(50)

This is the quick, more efficient variation of classic column chromatography, applying small extra pressure Its principle: the lower particle size (40-63 μm) of the adsorbent makes formation of the equilibrium much faster

Conditions:

- outside extra pressure in order to prevent resistance caused by lower particle size

- R_f value of the compound to-be-purified: 0.3-0.4 - R_f difference of the components must be greater,

than 0.1

-ΔC_v: 2-3 (ΔC_v=1/R_f;A-1/R_f;B)

„Flash” column chromatography

(51)

(52)

(53)

Method using instrument, controlled by computer

- Flowing the eluent with extra pressure (1-35 MPa) - Efficient fillings of the columns

Silica gel with low particle size (2-40 mm), Al

₂

O

₃

,

porous carrier covered by liquid, silica gel hydrofobized by alkylation

- Chance for gradient elution - Automatic detection

- Analytical and preparative application

High Performance Liquide Chromatography (HPLC)

(54)

Fundamental parts of the equipment:

- pump – demand: flowing free of fluctuation - using sampler – applying two-way valve - column – made of thick glass or steel tube

size: 1-5 mm x 10-30 cm (analytical); diameter>10 mm (preparative)

- detector – by UV, by refractivity, by conductivity, by MS, by fluorescence

- (fraction collector)

High Performance Liquide Chromatography (HPLC)

(55)

Origin of impurities:

- Side products prepared during the synthesis - Decomposition due to storing (by light, by air)

- Decomposition caused by storing (reaction with the material of the container, by humidity of air)

Solvents with appropriate quality are needed for the given purpose E.g.,

- There is no need to use anhydrous solvents for extraction, however, the solvent must not contain volatile impurity

- The eluent for chromatography must not contain solvent with different polarity (eluent with high purity is needed for HPLC)

- Anhydrous solvent is needed for water sensitive reactions (e.g., for Grignard reaction) Solvents with various purity can be bought, but frequently further purification is needed - Point of views of economy (factor of price)

- How to avoid contamination during storing

Purity of solvents

(56)

Peroxides are formed in ethers or alcohols during storing, due to light and/or oxygen

Peroxides are extremely explosive!

Checking peroxides:

-by test strip

-by adding KI reagent dissolved in hydrochloric acid, in the presence of starch:

it turns to be blue in the presence of peroxides

Methodes for removal of peroxides:

1. Boiling in the presence of SnCl₂

2. Extraction by FeSO₄ dissolved in sulfuric acid or FeCl₂ dissolved in hydrochloric acid

3. Extraction by Na₂SO₃ solution

4. Chromatogrphy/filtration through column filled with Al₂O₃ 5. mixing with LiAlH , or with CaH

Removal of peroxides

(57)

Purification of sulfanilamide 1

_O ^NH_S ²_O Recrystallization

NH₂ M_r: 172.20 mp.: 165-166 ^oC

1 Preparation of the saturated solution:

Dissolving it in water with heating.

2 Clarification:

Stop the heating, wait for 1 min, add charcoal, boil it for 2 min

Filtration:

Filter the hot solution through fluted filter paper

3

Impurities: 5-8 % acetanilide and 1-2 % N-acetylsulfanilamide

(58)

Purification of sulfanilamide 2

_O ^NH_S ²_O Recrystallization

NH₂ M_r: 172.20 mp.: 165-166 ^oC

4 Crystallization: Cool the filtrate with cold water bath

water pump

5 Suction filtration:

Büchner funnel, washing with cold water.

6 Drying: in the air.

7 Qualification: mp., TLC

Impurities: 5-8 % acetanilide and 1-2 % N-acetylsulfanilamide

(59)

Separation of o- and p-nitrophenol 1

Column chromatography

1

2 Input of material:

When silica gel has been settled, put filter into the top of the column, add concentrated solution of the mixture into the filter.

Preparation of the column:

Put filter into the bottom of column.

Suspend silica gel in CH₂Cl₂, pour to the column.

OH

NO₂

HO NO₂

o-nitrophenol p-nitrophenol MW: 139.11 MW: 139.11

mp: 46^oC mp: 114^oC

R_f: 0.85 (CH₂Cl₂) R_f: 0.18 (CH₂Cl₂)

(60)

Elualation, collection of the fraction:

let trough CH₂Cl₂on the column, complete from separatory funnel . Collect the dropping solution into test tubes.

(elualation of o-nitrophenol)

After the washing of o-nitrophenol continue the eluleation with the 1:1 ratio mixture of MeOH-CH₂Cl₂ (eluleation of p- nitrophenol).

Separation of o- and p-nitrophenol 2

Column chromatography

4 3

The controll of the purity of the fraction with TLC.

OH

NO₂

HO NO₂

o-nitrophenol p-nitrophenol MW: 139.11 MW: 139.11

mp: 46^oC mp: 114^oC

R_f: 0.85 (CH₂Cl₂) R_f: 0.18 (CH₂Cl₂)

(61)

Purification of ethyl acetate

H₃C C O O

C H₂ C H₃ M_r: 88.11

Bp. 76-77 ^oC n²⁰_D: 1.3723

ρ: 0.90

1 Extraction:

1. 5% Na₂CO₃ solution 2. 3x water

(CO₂!

Ethyl acetate is the upper layer)

Extraction and distillation

2 Drying: with CaCl₂ 20minutes

Filtration:

4 Distillation: main fraction between 73-79^oC.

3

Impurities: 5-10% ethanol and acetic acid

(62)

Name of the preparation

date Reaction equation

Molecular mass and quantity (also in Mols) of the compounds measured in; physical constants of the compounds (mp, bp, density, refractivity)

Short summary of the experiment, drawing of the equipments, remarks how to prevent fire, explosion, or accidents.

Critical steps.

Observations (color changes, warming by itself, etc.) in details.

Characterization of the product. Its appearence(state, color, smell)

Yield with mass in grams and with %.

Mp., bp., Rf by TLC, spectral data.

Sample for laboratory note-book

Role of laboratory note-book: summary of the data needed for the reproduction of the experiment.

(63)

Preparation of sulfonate ester (tosylation, S_NAc)

2-Naphthyl 4-toluenesulfonate 2-Naphthyl tosylate

4-toluenesulfonyl chloride naphth-2-ol 2-naphthyl 4-toluenesulfonate tosyl chloride (TsCl) 2-naphthyl tosylate

CH₃ S

O O

Cl

O H

CH₃ C

H₃

N

CH₃

+

C H₃

S O

O O

MW: 190.64 MW: 144.17 MW: 298.36

mp: 71ôC mp: 123-4ôC mp: 124-6ôC

MW: 101.19 bp: 88-9^oC

d: 0.726 CH₂Cl₂, r.t. 1 hour

(64)

Cl

O O S O

Cl

benzenesulfonyl chloride

OH

O O S O

OH

O O

CH₃ O S O

O CH₃

methyl benzenesulfonate

2-naphthyl 4-toluenesulfonate 2-naphthyl tosylate

Nomenclature

S O

O O 1

2

benzoic acid benzenesulfonic acid benzoyl chloride

methyl benzoate

(65)

S

_N

Ac reaction

nucleophilic substitution taking place on an acyl carbon

alcohol acid halide tetrahedral ester (nucleophilic) (electrophilic intermediate

carbon)

R O

H Cl

O

R₁

δ+

δ−

O R

H

O

Cl

R₁

R O

O

R₁

+

^H^Cl

(66)

attack of a nucleophile chloride – detachment of the leaving group

deprotonation of oxonium ion sulfonate ester

Analogous process: mechanism of tosylation

R O

H

Cl S O

O

CH₃

δ+

δ−

δ− _Cl

S O

CH₃ R O

H O

R O H

S O

O

CH₃ S CH₃

O

O O R

B

+

^B-H

(67)

R R S S_N2

retention inversion

Tosyl group is a „good leaving” group, in S

_N

2 reaction

substrate with stereogenic center

C

CH₃ CH₃

O H

H

C

CH₃ CH₃

O

H

Ts

H C

CN CH₃

C H₃

TsCl base

K CN

(68)

TS

Nu

^-

: -OH, N

₃

. Hlg LG: leaving group

Nu C

R₂

LG Nu

R₁ H

R₂

C

R₁ LG H

R₂

C R₁

Nu H LG

(69)

intermediate

reaction coordinate E

S

_N

2 S

_N

1

≠

≠₁

≠₂

(70)

S

_N

2 Suzuki cross-coupling

KCN KI

HNR¹R² ArOH

R-CH₂-I

R-CH₂-NR₁R₂ R-CH₂-OAr

R-CH₂-OTs R-CH₂-CN

Ar'-OTs Ar'-Ar"

Ar"B(OH)

₂

[Pd], base

(71)

1

Dissolve the solid material precipitated from the reaction mixture by adding water.

Measure 2-naphthol,

2

dichloromethane and triethylamine, and add tosyl chloride in 3

portions with cooling and stirring. Stir it for 1 hour at room

temperature.

Reaction

(72)

Separate the two-

4

phase mixture, extract the phase with dichloromethane by water.

3

Dry the organic

phase with Na₂SO₄.

Isolation of the product

(73)

Distil dichloromethane by rotational vacuum evaporator.

5

6 Recrystallize the distillation residue by boiling it in ethanol.

Purification of the product vacuum

(74)

7

Filter the crystals by vacuum filtration.

to the vacuum pump World of Molecules: Hints for practices

(75)

Sources of danger

: 1. Reagents:

2-naphthol – do not breathe the vapors, do not contact with skin tosyl chloride – is a compound with characteristic odor, caustic agent (protective gloves is obligatory).

triethylamine – is a liquid with characteristic odor, do not breathe the vapors, do not contact with skin.

2. Protective gloves and protective glasses are obligatory for each step of the reaction.

(76)

4,5-Dichloropyridazin-3(2H)-one

Pyridazine synthesis

M_r: 168.69 Mp: 127 ^oC

hydrazine hydrate mucochloric acid

(Z)-2,3-dichloro-4-formylprop-2-enoic acid HO

Cl O

Cl

H O

CH₃COOH -H₂O

4,5-dichloropyridazin-3(2H)-on NH₂ H₂O

NH₂

HN N

O

Cl

M_r: 164.97 Mp: 200-201 ^oC M_r: 50.06

ρ: 1.032

(77)

R O

R' H2N R''

R C O R'

N H H

R' R C

OH R'

N H

-H⁺/+H⁺ R' +H⁺/-H⁺

R C R'

N R'

hemiaminal Schiff base

(N-substituted imine)

H2N NHR' R

O R'

+

hydrazone R C

R'

N NHR'

-H2O R: alkyl, aryl

R': alkyl, aryl, H R'': alkyl, aryl

HN N

O

Cl Cl Schiff base structure unit

HN N

O

Cl Cl Hydrazone structure unit

(78)

R O X NH₂ R'

-H⁺/-X^-

H₂N NHR' R

O X

+ R: alkyl, aryl

R': alkyl, aryl, X: halogen,

HN N

O

Cl Cl Amide structure unit

HN N

O

Cl Cl Hydrazide structure unit

OC O

R

C N

X RO R'

H H

R O NHR'

R O

NHNHR' amide

hydrazide

(79)

Mechanism

HO

Cl O

Cl

H O

N NH₂

H H

N N

Cl

Cl H HO O

H O

O

HO Cl

Cl

HO

Cl O

Cl HO

N H

NH₂ H

HO

Cl O

Cl N

H₂N δ+

δ+

HN N

O

Cl

A_N E

S_Ni

-H₂O

-H -H /-H

N N

OH Cl

Cl

lactam lactim

(80)

HO

R² O

R¹

R3 O

HN N

O R¹

R² R³ NH2

NH₂ + NH2 + NH₂

N N

R³ R¹

R² R⁴ O

R² R³

R¹

R⁴ O

NH₂ + NH2

HN N

O R¹

R² OH HO

R² O

R¹

O HO

O O

O

R¹

R² NH₂

NH2 + HN

N O

R¹

R² OH

(81)

N N

N

O

MINAPRINE (Antidepressant)

N N

O O

N

O

EMORFAZONE (Antiinflammatory)

N NH₂

O H

N N

AZANRINONE (Cardiotonic)

Some pharmacologically active pyridazine derivative

(82)

1

In the flask place

2

mucochloric acid and acetic acid; in the dropping

funnel place

hydrazine hydrate.

Heat the mixture to 50 ºC. (Stirring, oil bath.)

Lift the flask out of the bath, add hydrazine hidrate dropwise during stirring.

(approx. 3 minutes) World of Molecules: Hints for practices

(83)

3

Heat and stir the

4

mixture for 15 minutes on an iol bath of 120 ºC-os.

Cool the mixture to 80 ºC, add water during stirring.

(Crystallization) World of Molecules: Hints for practices

(84)

Water pump

5

6

Let it stand for 15 minutes in an ice bath.

Filter the crystals out, wash them with water till neutral, dry them on air.

7

Check the purity of the

product by thin layer chromathography.

(85)

Safety:

1. Hydrazine hydrate is highly corrosive, toxic and flammable!

Use protective gloves!

Do not use flame!

2. The product may cause allergy. Avoid contact with skin, do not breathe its powder in!

3. Use protective gloves and glasses for every operation!

(86)

HN N

O Cl

Cl

ν_ass.N-H ν_ar.C-H hydrazideC=O νass. H-O

νacidC=O νolefinC=C

O Cl

Cl O

O H

1 2 3 4

4,5-Dichloropyridazin-3(2H)-one

Mucochloric acid

(87)

Mucochloric acid

4,5-Dichloropyridazin-3(2H)-one

1 2

3 4

N H

N O

Cl

5 Cl

6

H-6

H-4

OH

O Cl

Cl O

O H

1 2 3 4

(88)

1 2

3 4

N H

N O

Cl

5 Cl

6

C-3 C-5

C-6

C-4

C-1 C-3 C-2

O Cl C-4

Cl O

O H

1 2 3 4