查看完整版本 : IUPAC NAME

chris2009317 2013-7-7 08:04 PM

IUPAC NAME

A) 4-Methylpentane

B) 2-ethyl-2methylpropane

chungkin81 2013-7-7 08:22 PM

What do you want to ask?

chris2009317 2013-7-7 08:45 PM

[quote]原帖由 [i]chungkin81[/i] 於 2013-7-7 08:22 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=366570795&ptid=22151038][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]
What do you want to ask? [/quote]

Explain why the name given for each of the following alkanes is not the correct IUPAC name .Then give the correct IUPAC name for the compound

chungkin81 2013-7-7 08:55 PM

Hint:
Draw the structure by the given name in the question and then write the correct name by looking at the structure.

chungkin81 2013-7-7 10:05 PM

For example:
The structure of A (4-methylpentane) is as attached
The correct name for structure A is 2-methylpentane (use the lowest number)

chris2009317 2013-7-7 10:07 PM

is use bond-line formula or condensed formula?

chungkin81 2013-7-7 10:09 PM

It doesn't matter.
The first step is to draw the structure out first, and then use the corrrect naming rules to name the compound.

chris2009317 2013-7-7 10:16 PM

but, B) have three carbon , can not use use the lowest number

CH3------CCH2CH3CH3------CH3

chungkin81 2013-7-7 10:23 PM

B) 2-ethyl-2-methylpropane
First, the root word is propane
So, you should first draw like

     C --  C -- C

Then, consider the substituents 2-ethyl and 2-methyl, and you would draw this structure
                CH2CH3
                |
     H3C -- C -- CH3   
                |
                CH3

chungkin81 2013-7-7 10:30 PM

The name 2-ethyl-2-methylpropane is wrong because the longest carbon chain has 4 carbon atoms. (The carbon in bold red colour)
                [b][color=#ff0000]C[/color][/b]H2[b][color=#ff0000]C[/color][/b]H3
                |
     [color=#0000ff]H3C[/color] -- [b][color=#ff0000]C[/color][/b] -- [color=#0000ff]CH3[/color]   
                |
                [b][color=#ff0000]C[/color][/b]H3


There are 2 methyl ([color=#4169e1]CH3[/color]) substituents at the 2 position (count from the bottom as 1 for those carbon atoms marked in red colour).
So the correct name is 2,2-dimethylbutane.

[[i] 本帖最後由 chungkin81 於 2013-7-7 10:46 PM 編輯 [/i]]
頁: [1]
查看完整版本: IUPAC NAME