[avijit]

 reaction between metallic copper and gaseous ammonia?

[DevaDevil]

you are asking which reaction will/might take place?

pure copper, pure ammonia (g), without any other chemicals present will do nothing.

with an oxidiser present (oxygen) it may dissolve the topmost copper-oxides and create copper-ammonia complexes.

[ajkoer]

FYI, per Watt's "Dictionary of Chemistry and other allied sciences", page 138 (an online Google book), aqueous ammonia (which I take to mean cold liquid NH3) is decomposed in the presence of finely divided Cu (or Platinum) and air (or oxygen) into "nitride of ammonia" and other gases.

[ajkoer]

The link below is a 2008 article on the oxidation of NH3 with O2 in the presence of a Bimetallic CuO/CeO2 Nanoparticle Catalyst authored by Chang-Mao Hung, Taiwan, Republic of China:

http://www.aaqr.org/VOL8_No4_December2008/7_AAQR-08-07-OA-0031_447-458.pdf

To quote "The catalytic oxidation of ammonia has been reported to precede as follows the exothermic global reactions:

4NH3 + 3O2 → 2N2 + 6H2O +1266 KJ (1)
2NH3 + 2O2 → N2O + 3H2O +1102 KJ (2)
4NH3 + 5O2 → 4NO + 6H2O +904 KJ (3)

The SCO process that involves ammonia should be selective for nitrogen (reaction 1), and prevent further oxidation of nitrogen (reactions 2 and 3)"

What I find fascinating is how the original reference in Watt's Dictionary of Chemistry, over a century old, has been updated from the oxidation of ammonia in the presence of "finely divided copper" to a bimetallic CuO/CeO2 nanoparticle catalyst.

On the discussion as to whether the ammonia reference in Watt's is NH3 or NH4OH, there are some recent papers citing wet oxidation of ammonia, so the point appears to be mute. For example, the link below brings up a pdf dated April 2010 entitled "CATALYTIC WET AIR OXIDATION OF AQUEOUS SOLUTIONS OF AMMONIA IN A CONTINUOUS-FLOW TRICKLE-BED REACTOR OVER METAL SUPPORTED ON CARBON MATERIALS" by Chang-Mao Hung1,* and Wei-Bang Lin2

The metal referred to is Cu-activated carbon fiber (ACF) catalyst.

http://doc-0o-a0-docsviewer.googleusercontent.com/viewer/securedownload/99khlruld95bsluge9k6kgl3ghmn47pt/l1vea06fcvde0fn99mq7lumau6p6nvlo/1303398000000/Ymw=/AGZ5hq-pkpCmUrNYl8q6aMGpqnrW/QURHRUVTak1BeFMtOV81N2F1OGdiSHVmbjBaek1kTEFmYTBEcE4wT1J5bmIyZEpGSEdwbjNCUlpMdzctTldOOVA1TzgxQnkyMlF2UkU0dm1ZX0tMSGx4MnJRQXZhQzhVblUxdzhhaDUtVktqRS1SdnJsemlCb2hlekJkUklqN3B4SVB3OEgwRS04WHA=?a=gp&filename=J.+Environ.+Eng.+Manage.,+20(4)+251-255+(2010).pdf&chan=EwAAAHSe7frKnh2YqI1fiSY9pmh2TbEn1X2a/p/riYx%2BbP12&docid=1ebcc0e722e4c122581cc1340e9dfc0f&sec=AHSqidahBie2GrBh7iIL5QDMqufRZrk28supTuCgKJ_vVzc7iQDxWKxg_YJhytecr1_0kUa_a-_73drcmNaEnUyDoXRREO4BEDpFZcok-4KAO3NPD77SeAip1a1iLIpyi8zvmc86DsTH2NNaojf7fdxiC1i2wF6tZG2N91FZNN8zLV13fkG894CbE7GtSid-iHHAizBHYxFfp1EYa3Q1kuQrn4fcAKPeWZ2C-MBOHuV3kYamIEFkDY9W3NOKO9M2n6VQ6yDewNzMYkc78FCwViMcdWR91a-A5_U2qTdNhyuEgaJf6wpdD15PlXawPJXcl33O57usZ3PR&nonce=vsr9rmsf28a1m&user=AGZ5hq-pkpCmUrNYl8q6aMGpqnrW&hash=178d9d283i1adom9p1sgqqci4fq4tm7j
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[ajkoer]

Hi:

 I actually saw a video of a hot copper wire suspended over NH4OH (but not touching).

 The reaction was exothermic with the wire consumed and becoming brittle and falling into the solution.

 As apparently the decomposition of NH3 is exothermic, the copper is converted into CuO and falls apart.