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Posted by **rebekah** on Sunday, October 24, 2010 at 5:57pm.

Posted by rebekah on Sunday, October 24, 2010 at 4:48pm.

Give the general formula for any dialkene; that is, a straight-chain 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

cH3-cH2-cH=cH-cH=cH2

note on the ends, there are 3H

one each double bond, each C has one less H (each side)

CnH(2+2n-4) check that above n=6, byt this formula C6H10 counting... 6c, 10H

now the check

CH2=CH-CH2-CH=CH2

formula: C5H8

count: C5H8

CnH(2n-2) 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. CnH2n-2.

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 CnH2n-2.

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 CnH2n-2. 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 dont know how to make that into the di part of dialkene

- chem-repost -
**bobpursley**, Sunday, October 24, 2010 at 5:59pmWEll, both of us showed you, I am sorry it is marked wrong.

- chem-repost -
**rebekah**, Sunday, October 24, 2010 at 6:14pmbut. 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 CnH2n-2. 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 dont know how to make that into the di part of dialkene"

is there anyone else that knows the answer?

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