Notam formula hidrocarburii: CxHy
NE=[2+x(4-2)+y(1-2)]/2=2
4=2+2x-y => y=2x-2
f.m: CxH2x-2
deoarece reactioneaza cu r. Tollens
=> alchina cu tripla legatura marginala
CH≡C-(CH2)(n-3)-CH3 + [Ag(NH3)2]OH -> AgC≡C-(CH2)(n-3)-CH3 + 2NH3 + H2O
CxH2x-2 + 2Br2 -> CxH2x-2Br4
mCxH2x-2/mBr2=1:8
Malchina=12x+2x-2=14x-2
consideram un mol de hidrocarbura
1mol..........2moli
CxH2x-2 + 2Br2 -> CxH2x-2Br4
1mol..........2moli
n=m/M => m=n*M
malchina=14x-2
mBr2=2*160=320
14x-2/320=1:8
14x-2=320/8=40 => 14x=42 => x=3
alchina: propina