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UV Spectra Interpretation

UV Spectra Interpretation. Lecture #2. Dapatkan kedua senyawa berikut dibedakan dengan menggunakan spektrum UV?. Senyawa A: Sistem induk 217 nm Substituen alkil 20 nm Ikatan rangkap exo 5 nm  maks ( heksana ) 242 nm. Senyawa B: Sistem induk 217 nm

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UV Spectra Interpretation

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  1. UV Spectra Interpretation Lecture #2

  2. Dapatkankeduasenyawaberikutdibedakandenganmenggunakanspektrum UV? Senyawa A: Sisteminduk 217 nm Substituenalkil 20 nm Ikatanrangkapexo 5 nm  maks(heksana) 242 nm Senyawa B: Sisteminduk 217 nm Substituenalkil 15 nm Ikatanrangkapexo 0 nm  maks(heksana) 232 nm

  3. Hitung maks(heksana) untuksenyawaberikut: Senyawa : Sisteminduk 217 nm Dienahomoanular 36 nm Substituenalkil 20 nm Ikatanrangkapexo 0 nm  maks(heksana) 273 nm

  4. Hitung maks(heksana) keduasenyawaberikutdenganmenggunakanspektrum UV. Senyawa : Sisteminduk 217 nm Dienahomoanular 36 nm Substituenalkil30 nm Ikatanrangkapexo 15 nm Perpanjangansistem 60 nm  maks(heksana) 358 nm Senyawa : Sisteminduk 217 nm Dienahomoanular72 nm Substituenalkil30 nm Ikatanrangkapexo 5 nm Perpanjangansistem 60 nm  maks(heksana) 384 nm

  5. b b O  x Similar for Enones 227 239 202 215 Base Values, add these increments… b g  d,+ X=H 207 X=R 215 X=OH 193 X=OR 193 With solvent correction of….. Water +8 EtOH 0 CHCl3 -1 Dioxane -5 Et2O -7 Hydrcrbn -11

  6. Contoh Senyawa : Sisteminduk 215 nm Substituen beta (1x12) 12 nm Substituen delta (1x18) 18 nm Exo.DB 5 nm Perpanjangansistem 1 x30 30 nm  maks(etanol) 280 nm

  7. Hitung maks(etanol) senyawa-senyawaberikut: A D E B F C G

  8. AbsorpsiMaksimumLingkarBenzena Z = alkilatausisalingkar 246 nm Z= H 250 nm Z=OH atau O alkil 230 nm Tambahansubstituen R=alkilatausisalingkar o-,m- 3 nm p- 10 nm R=OH, Ome, O-alkil o-, m- 7 nm p- 25 nm R=O o- 11 nm m- 20 nm p- 78 nm R=Cl o-, m- 0 nm p- 10 nm R=Br o-, m- 2 nm p- 15 nm R=NH2 o-, m- 13 nm p- 58 nm R=NHAc o-, m- 20 nm p- 45 nm R=NHMe p- 73 nm R=NMe2 o-, m- 20 nm p- 85 nm

  9. Contoh.

  10. Generally, extending conjugation leads to red shift “particle in a box” QM theory; bigger box Substituents attached to a chromophore that cause a red shift are called “auxochromes” Strain has an effect… max 253 239 256 248

  11. Interpretation of UV-Visible Spectra • Transition metal complexes; d, f electrons. • Lanthanide complexes – sharp lines caused by “screening” of the f electrons by other orbitals • One advantage of this is the use of holmium oxide filters (sharp lines) for wavelength calibration of UV spectrometers. See Shriver et al. Inorganic Chemistry, 2nd Ed. Ch. 14

  12. Benzenoid aromatics UV of Benzene in heptane From Crewes, Rodriguez, Jaspars, Organic Structure Analysis

  13. Substituent effects don’t really add up Can’t tell any thing about substitution geometry Exception to this is when adjacent substituents can interact, e.g hydrogen bonding. E.g the secondary benzene band at 254 shifts to 303 in salicylic acid In p-hydroxybenzoic acid, it is at the phenol or benzoic acid frequency

  14. Heterocycles Nitrogen heterocycles are pretty similar to the benzenoid anaologs that are isoelectronic. Can study protonation, complex formation (charge transfer bands)

  15. Quantitative analysis Great for non-aqueous titrations Example here gives detn of endpoint for bromcresol green Binding studies Form I to form II Isosbestic points Single clear point, can exclude intermediate state, exclude light scattering and Beer’s law applies Binding of a lanthanide complex to an oligonucleotide

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