DBE: S with6 valences, thereforeformula and structruredoesnotprovidethesameanswer!

Homework 1

Calculate sildenafil’s (Viagra) M, elemental composition, DBE!

What kind of isomers can it have other than constitutional, draw one example!

M=1 449; C 54,7 %, H 5,22 %, Cl 4,89 %, N 8,7 %, O 26,5 % Calculate the compound’s molecular formula and DBE!

Tautomers

DBE: S with 6 valences, therefore formula and structrure does not provide the same answer!

m(H)=75.6, N(H) =76 not true, have to divide with 1.01!!!

DBE cannot be half for „normal” molecules

O

O O

CH ₃

2-tetralone

1-tetralone 3-methyl-benzofurane

Homework 2

O

CH ₃

 _C=O = ?

O

O  _C=O = 1683 cm ^-1

 _C=O = 1716 cm ^-1

Conjugation decreases

C=O bond order!

IR in practice

1. Verification

Attention: spectrum is dependent on polyforms!!

2. Structure elucidation: functional groups 3. Quantitation

4. Reaction monitoring (in-line sonda )

Famotidin A módosulat

20 40 60 80 100

%T

Famotidin B módosulat

20 40 60 80 100

%T

1000 2000

3000

Wavenumbers (cm-1)

N

H₂ N N

S S N

NH₂ S

O O

NH₂ NH₂

Polymorphism in IR

Particle size also matters!

Transmission

Solid phase: KBr pastille

Oil/Liquid: in nuyol/directly/dissolved-evaporated

Reflection: ATR head

(attenuated total reflectance)

Diamond, ZnSe

Amount: cca 1mg

The measurement is non-invasive, but with routine sample

preparation it is difficult to get back the material.

Two beam IR spectrometer

2DX=n l reinforce

2DX=(n+1/2) l cancel

FTIR spectrometer

Detector signal

Spectrum

FT: Monocromatic wave

FT: more waves

Optical retardation Nine wavelengths

Frequency Spectrum

consisting of 9 single frequencies Optical retardation Resulting detector signal:

Interferogram to spectrum

Background spectrum

Fourier transformation

500 1,000

1,500 2,000

2,500 3,000

3,500 4,000

Wavenumber, cm^-1

0.100.200.300.40

Single-channel intensity

Optical retardation

Detector signal

Fourier transformation

500 1,000

1,500 2,000

2,500 3,000

3,500 4,000

Wavenumber, cm^-1

0.100.200.300.40

Optical retardation

Sample spectrum

500 1,000

1,500 2,000

2,500 3,000

3,500 4,000

Wavenumber, cm^-1

0.100.200.300.40

Single-channel intensity

500 1,000

1,500 2,000

2,500 3,000

3,500 4,000

Wavenumber, cm^-1

406080100

Transmittance [%] 20

Division

Stable Fast

Digital spectrum, easy to modify Sensitive

Advances of FTIR technique

Albert Abraham Michelson

Michelson (1852-1931) interferometer