Requirements for the MOLECULAR SYNTHESIS B.S. Degree

Get that shit tested or you might just end up hospitalized or even dead!!!!!


It is well known that λmax values tend to be related to the strength of the electronic power in the benzenoid system (). Since, the electronic transition in these compounds involves a general migration of electron density from the donor group towards the azo group, the greatest effect in terms of longer wavelength is achieved by placing the substituent in the positions ortho or para to the azo group for effective conjugation (; ).


Absorption spectra: The details of the visible absorption spectra of the dyes are summarized in . The synthesized dyes developed a colour ranging from yellow (λmax 436 nm) to orange (λmax 520 nm) in ethanol.

Off all the dyes, dye 2c gave the highest λmax value in all the solvents. This result can be attributed to the longer wavelength effect exerted by the N-phenyl group and the naphthalene moiety which has an electron donating property. Half-band widths of the absorption band in DMF were determined ().

Exploring M. To explore a different substance…

Method 1: Synthesis of 2-methoxy-5-nitrophenyl azo-4-hydroxynaphthalene: The 2-Methoxy-5-nitroaniline (4 g, 0.024 mole) was diazotized in 6 mL of concentrated sulph and 50 mL of water by adding 10 mL of sodium nitrite solution (0.02 mole) dropwise at a temperature of 0-5°C. After 30 min the diazotisation was complete which was verified by using a solution of 4-(N, N-dimethylamino) benzaldehyde which generates colour if undiazotized aromatic amine is still present. The excess nitrous acid was destroyed by adding (0.15 g, 0.003 mole) urea solution.

Sreenivasan, V. , 1 Jan 1972, (2), 304. 996 kB.

Keto-enol tautomerism: Keto-enol tautomerism is not only of utmost importance to the dyestuff manufacturer but is also important in other areas of Chemistry. Keto-enol tautomers not only have different colours, they also have different tinctorial strengths (and hence economics) and different properties e.g., light fastness (). Azo dyes 2a-b and 2e-f can exist as a mixture of several tautomeric forms as shown in .

Sreenivasan, V. , 1 Jan 1972, (2), 304. 996 kB.

Melting points were determined using the Thumbnail melting point instrument. Fourier Transform Infrared (FTIR) spectra were recorded on a Nicolet Averser 330 series spectrophotometer. The UV-visible spectra were recorded in 1 cm quartz cells on a Genesys 10s VL 200 series spectrophotometer. Dye purity was assessed by Thin Layer Chromatography (TLC) using Whatman 250 m silica gel 60AMK 6F plates as the stationary phase and ether/acetone (5:1 by volume) mixture as developing solvent. Characterisation data are shown in and .

Smythies, JR. , 1 Feb 1953, (12), 339–347. 72 kB.

The infrared spectra of dyes 2e and 2f showed a broad hydroxyl band at 3441-3459 cm-1 and C-O band at 1072-1113 cm-1. This suggests that these compounds are predominantly in the azo-enol form as opposed to the hydrazone-keto-form (ketohydrazone form). On the other hand, the infrared spectra of dyes 2c and 2d showed intense NH2 bands at 3418-3260 cm-1. This suggests that these compounds are predominantly in the amino-azo form, since the amino-azo colorants show no evidence of tautomeric behavior (). This is true because the imino grouping as shown by the equilibrium equations of 2c and 2d is very unstable. The infrared spectra of dyes 2a and 2b showed intense carbonyl bands at 1620-1680 cm-1. This suggests that these compounds exist exclusively in the hydrazone-keto form as opposed to the azo-enol form, in the solid state ().

Smythies, JR. , 1 Feb 1953, (12), 339–347. 72 kB.

Chemical and instrumental analysis: The proton nuclear magnetic resonance ('H NMR) spectra were obtained with a mercury-200BB spectrometer equipped with an Oxford wide bore magnet, sun 3/160 MHz based computer with an array processor and GE Omega 6.0 software for solutions in a deuterated chloroform as solvent. The chemical shifts were reported in ppm using tetramethylsilane (TMS) as the internal reference.