Karpichev, "Amidoximes as effective acceptors of acyl group," Theoretical and Experimental Chemistry, vol.
Popov, "O-nucleophilic features of amidoximes in acyl group transfer reactions," Russian Journal of Organic Chemistry, vol.
Afonin, "An unusually fast nucleophilic addition of amidoximes to acetylene," Mendeleev Communications, vol.
For this purpose and in the interest of making acrylic fabrics less hydrophobic, anionic dyeable, a facile, safe, and efficient pretreatment method in which a partial conversion of nitrile groups present in the fabrics into amidoxime groups has been reported [4].
Amidoxime is effective [alpha]-nucleophile and its O-nucleophilic characteristics revealed a unique capability of reacting with an acylating agent in the basic, neutral, and acidic media [8, 9].
The unique reactivity of a-nucleophile in amidoxime group and the high uptake of anionic dye in an acid medium due to the presence of this group in the amidoximated acrylic fabrics [4-7] has prompted us to study the viability of reactive dye fixation in an acid medium using different types with different structures so as to find out which mechanism of fixation would be suitable for this type of substrate.
FTIR spectra were made to further confirm the changes in the characteristic peaks of amidoxime groups present in the amidoximated acrylic fabrics after being dyed with reactive dyes.
The reaction of hydroxylamine hydrochloride with acrylic fabrics has partially converted some of the nitrile groups into amidoxime groups.
This shift indicates the involvement of amidoxime groups in the fixation mechanism as shown in Figures 7-9.
Peak assignment Modified Wavenumber ([cm.sup.-1]) acrylic fibers RB19 Modified acrylic fibers dyed with RB19 N-O stretching, 947 -- 930 amidoxime C=N stretching, 1594 -- 1575 amidoxime OH and N[H.sub.2] 3150-3550, -- Present with less stretching, broad intensity amidoxime CN stretching, 2243 -- 2243 nitrile S=O stretching, -- 1040,1140,1228 Present overlapped suffonic group with less intensity at 1228 C=O, C=C, -- 1500-1670 Present overlapped conjugated with less intensity carbonyl at 1659 with aromatic TABLE 3: FT-IR characteristic absorption peaks of modified acrylic fibers, RO16, and modified acrylic fabrics dyed with RO16.
This result reveals the viability of amidoximation of acrylic fabrics, as the presence of amidoxime groups in the fabric would increase its nitrogen content relative to the blank one (compare nitrile group that has one nitrogen atom and amidoxime group that has two nitrogen atoms).