Posted by rebekah on .
I ddin't know if anybody would look far down to page to help me answer my question but this is what was said so far.
Posted by rebekah on Sunday, October 24, 2010 at 4:48pm.
Give the general formula for any dialkene; that is, a straightchain hydrocarbon with two double bonds along the chain. (Type your answer using the format CnHn+1 for CnHn+1.)
I know just alkene would be CnH2n but im not sure how to make it with the dialkene.
can any1 help me?
thanks!!
chem  bobpursley, Sunday, October 24, 2010 at 4:58pm
draw some
cH3cH2cH=cHcH=cH2
note on the ends, there are 3H
one each double bond, each C has one less H (each side)
CnH(2+2n4) check that above n=6, byt this formula C6H10 counting... 6c, 10H
now the check
CH2=CHCH2CH=CH2
formula: C5H8
count: C5H8
CnH(2n2) Try that.
chem  rebekah, Sunday, October 24, 2010 at 5:02pm
oh. that wasn't the correct answer
chem  DrBob222, Sunday, October 24, 2010 at 5:42pm
Try some. The general formula for a dialkene is the same as the general formula for an alkyne isn't it. CnH2n2.
I wrote about six or 7 straight chain hydrocarbons, stuck a couple double bonds in each, added H atoms to make up the quadrivalent C each, and voila! All of them worked with CnH2n2.
chem  rebekah, Sunday, October 24, 2010 at 5:46pm
i tried the answer in my online hw and it said it was wrong. i am looking in my text book and CnH2n2. the answer you guys are saying is the formula for alkynes.
but i need to find the formula for dialkene.
the formula for just alkene is CnH2n. but i don't know how to make that into the di part of dialkene

chemrepost 
bobpursley,
WEll, both of us showed you, I am sorry it is marked wrong.

chemrepost 
rebekah,
but. i can tell its wrong because of what i stated:
"i tried the answer in my online hw and it said it was wrong. i am looking in my text book and CnH2n2. the answer you guys are saying is the formula for alkynes.
but i need to find the formula for dialkene.
the formula for just alkene is CnH2n. but i don't know how to make that into the di part of dialkene"
is there anyone else that knows the answer?