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| | From:  ·Steve· | Sent: 5/20/2006 6:11 PM |
10) That's right, the main chain is decane. There are three different groups attached to the main chain, an ethyl group, an isopropyl group, and a methyl group. Since there is a group closest to the left end, we number starting from that end. The ethyl group is on carbon 3, the isopropyl group is on carbon 5, and the methyl group is on carbon 7. So, the name is 3-ethyl-5-isopropyl-7-methyldecane. 1) Correct 
2) This is 2,2-dibromobutane.
3) Correct 5) Correct
6) This is 4-ethyl-2-methyloctane. There is a methyl group on carbon 2 and an ethyl group on carbon 4. In the name, the groups are named in alphabetical order.
Whenever you have more than one of any group, you indicate the number with the prefixes di, tri, etc. For example, 1,2,3-trichlorobutane. This name tells us clearly that there are three chloro groups, and one is attached to carbon 1, another on carbon 2, and another on carbon 3. And of course that is the purpose of this naming system, to be able to tell with certainty what the structure of the molecule is, from the name.
Keep at it!
Steve |
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sorry deleted cuz it did not show up right. quick question CH3 ê CH2-CH2-CH2-CH2-CH2 ê CH3 wuld it matter wiyth this thing in between - each of them? my guess is that the name is 1, 5-Dimethyl Pentane oka as for my second question I have does it matter if it has brackets? like so in this one CH3-(CH2)6-CH-CH3<o:p></o:p> ê CH3 I um unsure thanks for your help! |
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| | | From: ·Steve· | Sent: 5/20/2006 9:11 PM |
>> my guess is that the name is 1, 5-Dimethyl Pentane << CH3 | CH2-CH2-CH2-CH2-CH2 | CH3 Ahhhh, they got you! That is simply heptane, CH3CH2CH2CH2CH2CH2CH3. Remember Rule 1, finding the longest carbon chain. Those two "methyl groups" are not named that way here because those carbons are simply part of the main chain. >> does it matter if it has brackets? << CH3(CH2)6CHCH3
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CH3
That is OK, it just condenses the structural formula a little more. This is 2-methylnonane. Unless there is a a really long CH2 repeat, I normally write all the CH2's just to make the structure as clear as possible.
CH3CH2CH2CH2CH2CH2CH2CHCH3
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CH3
Steve |
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| | | From: ·Steve· | Sent: 5/20/2006 9:18 PM |
BTW I hope the structures are showing properly on your computer. The character I'm using for the vertical bonds ( | ) is on the keyboard, just under the backspace key on mine. And hopefully the atoms are lining up correctly so those bonds are attached to the right atoms! Let me know if the structures are not lining up right for you. Steve |
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hi there I as well am learning about naming alkanes and this has helped me alot! but I have one question myself.. um would it matter say if it has a c in the middle here i will give an example: CH3 l CH3-CH2-C-CH2-CH-CH2-CH3 l l CH2 CH3 l CH3 Would that not be the longest chain? I still don't understand how you would name that one? Okay so my guess for this is that it is called I really have no idea thanks for your help! |
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| | | From: ·Steve· | Sent: 6/1/2006 3:03 AM |
Hey, how's it going in the world of alkanes?  That's right, the longest chain has seven carbons which is heptane so that is the parent name. CH3 1 2 3| 4 5 6 7 CH3–CH2–C–CH2–CH–CH2–CH3 | | CH2 CH3 | CH3 Now which end to start numbering from, since there is a group attached to third carbon from either end, we break the tie by seeing which end a second group is closest to, which is the left end (there is a methyl group and an ethyl group attached to the third carbon from that end). The other methyl group is on carbon 5. So the alkane is 3-ethyl-3,5-dimethylheptane. BTW there is another chain that has seven carbons: CH3 3| 4 5 6 7 CH3–CH2�?/FONT>C–CH2–CH–CH2–CH3 | | 2 CH2 CH3 | 1 CH3 But this gives the same result, 3-ethyl-3,5-dimethylheptane, so it makes no difference in this case. For the group names, just memorize the common ones and that'll make things a lot easier! ––CH3 = methyl \ | These are the "big two" that you see most often. ––CH2�?/FONT>CH3 = ethyl / ––CH2�?/FONT>CH2�?/FONT>CH3 = propyl CH3 | ––CH–CH3 = isopropyl etc. Steve |
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okay I was wondering if you check for meif I was going in the right direction or not. okay i will attachet it. Thanks! |
| | chem! check1.doc |
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| | | From: ·Steve· | Sent: 6/11/2006 8:51 AM |
>> The number of covalent bonds formed by carbon is 90% <<
Not sure where the "90%" comes from, but carbon forms four covalent bonds. In any combination of four total bonds (four single, two single & one double, or one single & one triple) the carbon atom has a zero formal charge (let me know if you need a definition of that!).
>> Hydrocarbons are molecular compound containing only carbon and hydrogen atoms <<
That's correct.
>> Give the general formulas for alkanes, alkenes, and alkynes. <<
Alkanes: CnH2n+2
Alkenes: CnH2n
Alkynes: CnH2n�?
Correct.
>> Name the following alkanes. <<
1) CH3-CH2-CH2-CH2-CH-CH3
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CH3
1A = 2-Methyl Hexane
That's correct, 2-methylhexane.
2) CH3-CH2-CH2-CH-CH3
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CH2
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CH3
2A = 1-ethyl pentane
Oops, first check the structure; the "ethyl group" should be on the CH carbon, second from the end, not on the end CH3 carbon, Otherwise that CH3 carbon will have five bonds on it, a no-no. Here's what it should be, with the main chain highlighted:
CH3-CH2-CH2-CH-CH3
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CH2
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CH3
Remember Rule 1, finding the longest carbon chain; this is 3-methylhexane. Going back to the structure you first had, but correcting the hydrogens,
CH3-CH2-CH2-CH2-CH2
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CH2
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CH3
this is simply heptane, CH3-CH2-CH2-CH2-CH2-CH2-CH3. Don't be fooled by a crooked main chain, it does not have to be drawn as a straight horizontal chain, although that is usually the best.
Steve
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I am getting the hang of this is pretty simple after a while but there is still one that stumps me i attached my work and the one i don't understand thanks for your help! |
| | chem! check1.doc |
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| | | From: ·Steve· | Sent: 6/13/2006 7:40 AM |
c) CH3–CH–CH3 2�?Methyl Propane
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CH3 e) C9H20 Nonane Probably, but there are 35 structural isomers with formula C9H20 !  f) CH3�?CH2)6–CH3 Octane g) H H H H H
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H–C–C–C–C–C–H Pentane
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H H H H H
h) CH3
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CH3–CH2–CH2–CH2–CH 1–methylheptane
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CH2
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CH3
i) CH3
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CH3�?CH2)3–C–CH3 1, 1–dimethylhexane
| Make that 2,2-dimethylhexane.
CH3
j) CH3 CH3
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CH3–C–––C–CH3 This one I don’t get it is just confusing!
| | There was an extra bond at the top that I removed.
CH3 CH3 This is 2,2,3,3-tetramethylbutane. OK, coming along! Some of the bond alignments were off which may have caused a couple of the errors. Steve |
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okay i have a question how do I balance and complete theses reactions? a) CH3-CH2-CH3 (g) + Br2 (l) --> b) C7H16 (l) + O2 (g) --> c) CH3-CH2-CH2-CH3 (g) + CH3-CH3 (g) --> d) H H H<o:p></o:p> l l l <o:p></o:p> H¾C¾C¾C¾H + F2 (g) --> l l l H H H<o:p></o:p> Thanks for your Help! |
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k I will try again: H H H l l l H-C-C-C-H l l l H H H |
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| | | From: ·Steve· | Sent: 6/13/2006 7:50 PM |
a) CH3-CH2-CH3 (g) + Br2 (l) -->
This is called a substitution reaction in organic chemistry because the hydrogens in the alkane get replaced or substituted with halogen atoms, one at a time. If we start with replacing just one hydrogen, there are two possible products, 1-bromopropane and 2-bromopropane, with 2-bromopropane being the major product:
Br
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CH3CH2CH3 + Br2 ––�?gt; CH3CHCH3 + HBr
This kind of selectivity of the product is called regioselectivity in organic chemistry. The bromine bonds preferentially at one atom or "region" in the propane molecule. It turns out that the lowest energy reaction pathway (the reaction mechanism) leads to 2-bromopropane in this reaction.
b) C7H16 (l) + O2 (g) -->
Complete combustion of any organic compound containing the elements C, H, and/or O gives only the products CO2 and H2O. First balance the carbons, then the hydrogens, and lastly the oxygens by putting the necessary coefficient in front of O2.
c) CH3-CH2-CH2-CH3 (g) + CH3-CH3 (g) -->
There shouldn't be any reaction between two alkanes. In fact alkanes are generally unreactive. Their major reactions are halogenation (reaction 'a' above) and combustion. There are alkane "cracking" reactions that can occur between alkane radicals, but as written this does not look like one of those.
d) H H H
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H–C––C––C–H + F2 (g) -->
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H H H
This is just like reaction (a). The hydrogen atoms will get replaced by fluorine atoms in this case. A big difference with fluorination, compared to chlorination and bromination, is that reactions of alkanes with F2 are highly exothermic, even explosive, and as a result are difficult to control. We can give the monofluorinated major product 2-fluoropropane as we did in reaction (a). Assuming the C–C bonds survive, all of the hydrogens can be replaced with fluorine atoms, giving 1,1,1,2,2,3,3,3-octafluoropropane, or "perfluroropropane" :
H H H F F F
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H–C––C––C–H + 8 F2 (g) ––�?gt; F–C––C––C–F + 8 HF
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H H H F F F
The product you choose for fluorinations may depend on how your particular textbook and/or teacher presents them! Steve |
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