Bromomethyl Blue

By means of a pipette, transfer a portion of approx lOg of the sample to a tared 250 ml beaker, rewelgh and dissolve in 100ml of benzene. Move the soln to a 250-ml separatory funnel and shake the contents of it with a 50-ml portion of neutral distilled water. After separation of layers run die water layer into the above 250-ml beaker. Repeat the operation using another 50ml of discd w and transfer the bottom layer to the same beaker. Add to beaker several drops of bromomethyl blue indicator. If the soln turns yellow titrate immediately with standard 0.01N NaOH. soln and if hlue titrate immediately with standard 0.0IN sulfuric acid. The change of color is taken as end point. Run a blank detn on 100ml of benzene alone and correct die volume alkali of acid required for titration. Calculate the percentage of acidity as nitric acid or alkalinity as Na carbonate as follows ... 

The structure of the blue salt was based on its being hydrolyzed to give bromoacetone, but this could equally well be derived from a 2-bromo-methyl-4-methylbenzodiazepinium salt. An authentic sample of the latter salt was later prepared from equimolar amounts of 2,4-dimethylbenzodiazepine and bromine in chloroform [76JCS(P1)2353]. This product was blue, its structure was confirmed by its H NMR spectrum, and its melting point was similar to that of the earlier so-called 3-bromo derivative. It seems evident that the latter was in fact the 2-bromomethyl compound. 

When excited at 266 nm, all four compounds exhibited a broad blue fluorescence centered at a400 nm with lifetimes ranging from 100 to 3500 ps. Excitation with a second 355-nm laser pulse which was delayed relative to the first 266-nm pulse produced a fluorescence centered at V600 nm with a lifetime of vlO ns. Since the emission spectra (Figure 7) obtained by excitation of l-(chloromethyl)naphthalene and l-(bromomethyl)-naphthalene are superimposable in the region from 550 to 750 nm, this red fluorescence was attributed to the 1-naphthylmethyl radical. In a similar manner, the red fluorescence resulting from two-color excitation of 2-(chloromethyl)naphthalene and 2-(bromomethyl)naphthalene was attributed to the 2-naphthylmethyl radical. This two-color fluorescence technique used in conjunction with OMCDs has proven to be a powerful tool in the study of photodissociation of haloaromatic compounds. 

Figure 7. Two-color fluorescence spectra of the I-naphthylmethyi and 2-naphthyl-methyl radicals. Spectra were produced by excitation of the sample with a 25-ps, 266-nm laser pulse followed by a 25-ps, 355-nm pulse delayed by 60 ps. Key to (halo-methyljnaphthalenes a, I-(chIoromethyI)naphthaIene b, 2-(chloromethyl)naphthalene c, I-(bromomethyI)naphthalene and d, 2-(bromomethyl)naphthalene. Note the fluorescence in the blue region of Spectrum c is due to impurities that contaminated the sample of l-(bromomethyl)naphthalene (28).

Bromomethyl-6,7-dime thoxy coumarin 4-Bromomethyl-7-methoxycoumarin Calcein Blue AM... 

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