Synthesis and chemical reactions Chloramine

1 synthesis , chemical reactions

1.1 production
1.2 decomposition
1.3 reactions

synthesis , chemical reactions

nh2cl highly unstable compound in concentrated form. pure nh2cl decomposes violently above −40 °c (−40 °f). gaseous chloroamine @ low pressures , low concentrations of chloroamine in aqueous solution thermally more stable. chloroamine readily soluble in water , ether, less soluble in chloroform , carbon tetrachloride.

production

in dilute aqueous solution, chloroamine prepared reaction of ammonia sodium hypochlorite:

nh3 + clo → nh2cl + oh

this first step of raschig hydrazine synthesis. reaction has carried out in alkaline medium (ph 8.5–11). acting chlorinating agent in reaction hypochlorous acid (hocl), has generated protonation of hypochlorite, , reacts in nucleophilic substitution of hydroxyl against amino group. reaction occurs quickest @ around ph 8. @ higher ph values concentration of hypochlorous acid lower, @ lower ph values ammonia protonated form ammonium ions nh+

4, not react further.

the chloroamine solution can concentrated vacuum distillation , passing vapor through potassium carbonate absorbs water. chloroamine can extracted ether.

gaseous chloroamine can obtained reaction of gaseous ammonia chlorine gas (diluted nitrogen gas):

2 nh3(g) + cl2(g) ⇌ nh2cl(g) + nh4cl(s)

pure chloroamine can prepared passing fluoroamine through calcium chloride:

2 nh2f + cacl2 → 2 nh2cl + caf2

decomposition

the covalent n−cl bonds of chloroamines readily hydrolyzed release of hypochlorous acid:

rr′ncl + h2o ⇌ rr′nh + hocl

the quantitative hydrolysis constant (k value) used express bactericidal power of chloroamines, depends on generating hypochlorous acid in water. expressed equation below, , in range 10 10 (6990280000000000000♠2.8×10 monochloroamine):

k
=




c



rr

′


nh



⋅

c

hocl




c



rr

′


ncl







{\displaystyle k={\frac {c_{{\text{rr}} {\text{nh}}}\cdot c_{\text{hocl}}}{c_{{\text{rr}} {\text{ncl}}}}}}

in aqueous solution, chloroamine decomposes dinitrogen , ammonium chloride in neutral or mildly alkaline (ph ≤ 11) medium:

3 nh2cl → n2 + nh4cl + 2 hcl

however, few percent of 0.1 m chloroamine solution in water decomposes according formula in several weeks. @ ph values above 11, following reaction hydroxide ions occurs:

3 nh2cl + 3 oh → nh3 + n2 + 3 cl + 3 h2o

in acidic medium @ ph values of around 4, chloroamine disproportionates form dichloroamine, in turn disproportionates again @ ph values below 3 form nitrogen trichloride:

2 nh2cl + h ⇌ nhcl2 + nh+

4
3 nhcl2 + h ⇌ 2 ncl3 + nh+

4

at low ph values, nitrogen trichloride dominates , @ ph 3–5 dichloroamine dominates. these equilibria disturbed irreversible decomposition of both compounds:

nhcl2 + ncl3 + 2 h2o → n2 + 3 hcl + 2 hocl

reactions

in water, chloroamine ph-neutral. oxidizing agent (acidic solution: e° = −1.48 v, in basic solution e° = −0.81 v):

nh2cl + 2 h + 2 e → nh+

4 + cl

reactions of chloroamine include radical, nucleophilic, , electrophilic substitution of chlorine, electrophilic substitution of hydrogen, , oxidative additions.

chloroamine can, hypochlorous acid, donate positively charged chlorine in reactions nucleophiles (nu):

nu + nh3cl → nucl + nh3

examples of chlorination reactions include transformations dichloroamine , nitrogen trichloride in acidic medium, described in decomposition section.

chloroamine may aminate nucleophiles (electrophilic amination):

nu + nh2cl → nunh2 + cl

the amination of ammonia chloroamine form hydrazine example of mechanism (the raschig process):

nh2cl + nh3 + naoh → n2h4 + nacl + h2o

chloramine electrophilically aminates in neutral , alkaline media start decomposition:

2 nh2cl → n2h3cl + hcl

the chlorohydrazine (n2h3cl) formed during self-decomposition unstable , decomposes itself, leads net decomposition reaction:

3 nh2cl → n2 + nh4cl + 2 hcl

monochloramine oxidizes sulfhydryls , disulfides in same manner hypochlorous acid, possesses 0.4% of biocidal effect of hclo.