naming of carbon compunds (1 Viewer)

[ronaldinho]

c-c-c-c
|
c ----- the c supposed to be under the third carbon FROM LEFT TO RIGHT... for some reasno its not working...

The name for the above hydrocarbon is
2-methylbutane

They say, "longest carbon chain first". But can't you go from either left or right to get the longest carbon chain?

and then the book says about branches or side chains. How can you tell a side chain. Is there not three side chains in the above picture. Two one the side and one on the bottom (bolded in red)


1. The compound is named as a derivateive of the hydrocarbone corresponding to the longest carbon chain

2. The branches (side chains) are given as prefixes, and if there is more than one they are listend alphabetically

3. Numbers are used to denote to which carbon, of the longest chain, the side chains are attached; numbering beings from the end which reslts in the smallest numbers overall. - what does this sentence mean?

thanks for ur help!

 

[Riviet]

C-C-C-C
------|
------C

and


C-C-C-C
------|
------C

are both 4 carbons in length (see highlighted red C's), hence the name starts with "but-" either way.

3. Numbers are used to denote to which carbon, of the longest chain, the side chains are attached; numbering beings from the end which reslts in the smallest numbers overall. - what does this sentence mean?

The 2 in 2-methylbutanol specifies which carbon the methyl is is connected to (methyl is the branch consisting of 1 C and 3 H's in it). The underlined bit in the quote just means you number starting from the end that gives you smaller numbers. In your example, if we counted from left to right, the 3rd carbon would be joined to the methyl branch BUT if we counted from right to left, the 2nd carbon would be joined to the methyl. 2<3, so we call it 2-methylbutanol instead of 3-methylbutanol since we wanted smaller numbers according to the rule.

and then the book says about branches or side chains. How can you tell a side chain. Is there not three side chains in the above picture. Two one the side and one on the bottom

After the longest carbon chain is determined (highlighted in red in both models above), ONLY the parts in black become your chain(s), ie your chains can't be part of the longest carbon chain that you picked. In our example, there is only the one carbon that is not part of the longest chain specified earlier, so this becomes the chain.

 

[ronaldinho]

right right kk...

got it now
thanks for ur help man.. u explained it good unlike the book which feels that it has to use these bloody hard words to make u understand