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Offline portugal

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few organic chem questions i need help answering with
« on: August 23, 2007, 06:08:16 AM »
1. Compound A has a molecular formula C4H9Cl. Compound A reacts
with Y in ethanol to give 1-butene, which when reacted with
Br2/H2O gives compound B. Which of the following statements
is true?

a. B could be 1,2-dibromobutane and Y could be KOH

 b. A could be 1-chlorocyclobutane and Y could be H2/Pt

 c. B could be 1-bromo-2-butanol and Y could be KOH

 d. A could be 1-chlorobutane and Y could be H+

 e. B could be 2-bromo-1-butanol and Y could be H2/Pt


2. Which of the following compounds contain conjugated systems?

estrone; cycloocta-1,3,5-triene; 2-cyclopentenone; 3-buten-2-one; 2,5-dimethylhexa-2,4-diene

 a. all of the above

 b. estrone only

 c. 2-cyclopentenone only

 d. 2,5-dimethylhexa-2,4-diene only

 e. none of the above

Offline Yarr

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Re: few organic chem questions i need help answering with
« Reply #1 on: August 23, 2007, 07:05:39 AM »
1. I would addvise you to study alkene formation by elimination reactions, and addition reactions to C-C double bond.

2. Ask yourself "What is a conjugated system?", answer this question, and then look/write the structures of those compounds.

Offline portugal

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Re: few organic chem questions i need help answering with
« Reply #2 on: August 25, 2007, 08:42:16 PM »
does anyone agree with me that the answer to question 1 is option C???

Offline organic help

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Re: few organic chem questions i need help answering with
« Reply #3 on: August 26, 2007, 12:06:37 AM »
yeah, i think the answer to that is C.

Offline portugal

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Re: few organic chem questions i need help answering with
« Reply #4 on: August 26, 2007, 11:11:47 PM »
i am still having difficulty with the conjugated sytem question i posted. would any1 be able to help me solve it????

Offline Yggdrasil

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Re: few organic chem questions i need help answering with
« Reply #5 on: August 27, 2007, 12:51:10 AM »
What difficulties are you having?  Do you know what a conjugated system is?  Do you know what the structures look like?

Offline portugal

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Re: few organic chem questions i need help answering with
« Reply #6 on: August 27, 2007, 01:28:19 AM »
No i dont know what a conjugated system is really and as well as that i dont know what most of those strucutures look like such as estrone.. could you please help me with this i am really struggling as it is a question that is due in on friday. i dont want answers i want help

Offline macman104

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Re: few organic chem questions i need help answering with
« Reply #7 on: August 27, 2007, 02:45:19 AM »
Conjugated System
Estrone
Cycloocta-1,3,5-triene
2-cyclopentenone
3-buten-2-one (aka Methyl Vinyl Ketone)
2,5-dimethylhexa-2,4-diene

Google really is your friend.  All but the last two of these were found using google, and simply just plugging the exact names you gave me into the search engine.  Also, a good site for finding compounds is http://chemfinder.cambridgesoft.com/.  After you do a certain number of searches, you'll have to register, but it's free and it's a good resource, because it also provides other links with information about the compound, and alternative names for the compound you searched for.

Armed with those structures, and the first link of conjugated systems, what are your new thoughts on the problem you posed (after you've digested all of that info of course ;))

Offline portugal

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Re: few organic chem questions i need help answering with
« Reply #8 on: August 27, 2007, 03:01:23 AM »
does anyone believe that the answer is just  (d. 2,5-dimethylhexa-2,4-diene only )

Offline Yggdrasil

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Re: few organic chem questions i need help answering with
« Reply #9 on: August 27, 2007, 03:02:08 AM »
Why do you say that?

(note: I'm amused by the fact that the all of the above choice has nothing above it!)

Offline portugal

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Re: few organic chem questions i need help answering with
« Reply #10 on: August 27, 2007, 03:14:33 AM »
i say that because it is the only one that has alternating double and single bonds throughout its strucutre becuase ones such as estrone and cyloocta dont have this alternating pattern thoughout their entire chain??? am i right about this otherwise if i am not right then i might say all of the above possibly becuase it might not need to go around the entire way the alternating pattern...i am not sure

this is what happens when you go to australian universities lol, u get questions u dnt even no or have covered in lectures

Offline Yggdrasil

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Re: few organic chem questions i need help answering with
« Reply #11 on: August 27, 2007, 03:28:39 AM »
I would say that the alternating single-double bonds don't have to throughout the entire structure to say that it contains a conjugated system.  Also, C=O double bonds can be conjugated to C=C double bonds as in the case of methyl vinyl ketone and 2-cyclopentenone.

In addition to knowing how to recognize a conjugated system, I would stongly suggest reading about conjugation in your chem book.  The wikipedia article doesn't really do a good job explaining how conjugation works in terms of molecular orbitals.

Offline sjb

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Re: few organic chem questions i need help answering with
« Reply #12 on: August 27, 2007, 04:15:02 AM »
Why do you say that?

(note: I'm amused by the fact that the all of the above choice has nothing above it!)

It's probably synonymous with "all the choices" :)

S

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