Sarahisme Posted May 30, 2005 Posted May 30, 2005 hey is the correct name for this (Z)-3-Ethyl-4-methyl-pent-2-ene or (E)-3-Ethyl-4-methyl-pent-2-ene i thought it'd be (E)... but yeah... what do you chemistry wizs' think?
Sarahisme Posted May 30, 2005 Author Posted May 30, 2005 actually i changed my mind, i think its (Z) because 1 and 4 (or those sorta points) are 'high' priority, and so it is (Z) or cis, since the high priorities are on the same side ??
BenSon Posted May 30, 2005 Posted May 30, 2005 (Z)-3-Ethyl-4-methyl-pent-2-eneor (E)-3-Ethyl-4-methyl-pent-2-ene Whats the difference? ~Scott
BenSon Posted May 30, 2005 Posted May 30, 2005 Doh I didn't even see the Z and the R Ok Z is when they are on the same side as the double bond E is the opposite. Argh it has been ages since I looked at this stuff but I think thats right. ~Scott
Sarahisme Posted May 30, 2005 Author Posted May 30, 2005 lol so it is (Z) then? cool you wouldnt know how to deal with double bonds and stuff when deciding whether it is Cis or trans (z or e)??
Sarahisme Posted May 30, 2005 Author Posted May 30, 2005 i.e. how do you decided whether something such as this molecule is cis or trans?
BenSon Posted May 30, 2005 Posted May 30, 2005 Jeez What is it with you and hard questions I haven't even finished high school Argh!. Ok now thats out of my system, Ok I can remember what to do once you know what the stereocentre is but I can't remember how to find the stereocentre, sorry. If you can tell me what that is I might be able to work it out. ~Scott
Sarahisme Posted May 30, 2005 Author Posted May 30, 2005 oh the cyral centre...hmmm hang on, i don't think it has a chiral centre (but i am really not too sure about that)
BenSon Posted May 30, 2005 Posted May 30, 2005 Ah don't worry I'm so stupid, stereocentre, I must be tried OK lets give this a shot. your right it has no chiral centre. I'm going to go with cis, only because the double bond to the left of the pic is common to both priority groups and the other isn't. So the priority, functional, whatever their called groups are on opposite sides. Lock it in eddie, cis, for $5,000. ~Scott
budullewraagh Posted May 30, 2005 Posted May 30, 2005 it is cis, as the double bonds come out on the same side
Sarahisme Posted May 31, 2005 Author Posted May 31, 2005 could you explain why abit more, i only get the basics of this this stuff, and yeah i don't own a textbook unfortuantly
budullewraagh Posted May 31, 2005 Posted May 31, 2005 well, consider the double bonds. first, the one on the right. see the horizontal plane made by the second and third carbon atoms from the right? both double bonds are on the same side of that plane
Bluenoise Posted May 31, 2005 Posted May 31, 2005 Are you sure about that? I pretty sure that the single bond between the double bonds rotates so there isn't a fixxed cis or trans for that structure.
Sarahisme Posted May 31, 2005 Author Posted May 31, 2005 hmm..interesting can anyone give me a link to a good site that explains this basic bit of organic chemistry? thanks Sarah
budullewraagh Posted May 31, 2005 Posted May 31, 2005 "Are you sure about that? I pretty sure that the single bond between the double bonds rotates so there isn't a fixxed cis or trans for that structure." could you substantiate that? http://www.organic-chemistry.org
Bluenoise Posted June 1, 2005 Posted June 1, 2005 I wish, but my nomenclature is horrible. Maybe someone else could find the name. But I know that that single bond is formed from two sp2 hybridized orbitals and acheives symmetrical overlap all the way around which allows it to rotate freely, making it only one structure. However there is a chiral centre present where at the carbon bonded to the nitrogen.
budullewraagh Posted June 1, 2005 Posted June 1, 2005 but that rotational motion doesnt necessarily affect the position of the doubly bonded carbon
Bluenoise Posted June 1, 2005 Posted June 1, 2005 but that rotational motion doesnt necessarily affect the position of the doubly bonded carbon Yes it does, all the positions of the orbitals on one carbon are fixxed relatively to each other, so as long as it does not fall on the axis of rotation the position will change when rotation happens on that axis. However, if there are other constraints like a ring or extreem steric interactions rotation may not be possible. This is not the case here though. Okay so I forced myself to do it. This is the IUPAC name of that structure 1-(3-vinyl-4,5-dihydrofuran-2-yl)ethanamine I put it through a sturctural analysing software. (http://www.acdlabs.com) I made it search for stero centers. Two exist the S and R at the chiral centre near the NH2. Not a cis and trans on the single bond separting the double bonds. All possible isomers for this structure: (1S)-1-(3-vinyl-4,5-dihydrofuran-2-yl)ethanamine & (1R)-1-(3-vinyl-4,5-dihydrofuran-2-yl)ethanamine
budullewraagh Posted June 1, 2005 Posted June 1, 2005 the orbitals aren't quite fixed. they're nearly fixed, i understand. nonetheless, the rotational motion of one of them does not cause the others to change position on any of the x,y, or z axes
Bluenoise Posted June 1, 2005 Posted June 1, 2005 the orbitals aren't quite fixed. they're nearly fixed, i understand. sure, same thing for our purposes, no need to nitpic. nonetheless, the rotational motion of one of them does not cause the others to change position on any of the x,y, or z axes I disagree. Not so much the rotation of the orbital but the rotation of the atom on an axis that passes through the orbital. The other orbitals will move. They are practically at fixxed angles and will stay approximatley in that arrangement if the atom is rotated. Anyways, the point of matter is that that bond does not create different stereo isomers.
YT2095 Posted June 1, 2005 Posted June 1, 2005 in the original pic it`s drawn as trans but surely it could be cis as the bond between 3 and 4 can rotate? 3-Ethyl-4-methyl-pent-3-ene would lock it into trans.
EwenM Posted June 1, 2005 Posted June 1, 2005 Cis and Trans: shouldn't they be reserved for cases where there are two hydrogen atoms on the same/opposite sides of the double bond (e.g. 1,2-dichloroethene)? E and Z were taught to me as superior to cis and trans because the CIP system clarifies which groups have priority. Cis and trans is a bit vague but OK with hydrogens.
chemi Posted June 2, 2005 Posted June 2, 2005 hey is the correct name for this (Z)-3-Ethyl-4-methyl-pent-2-ene or (E)-3-Ethyl-4-methyl-pent-2-ene i thought it'd be (E)... but yeah... what do you chemistry wizs' think? The answer should be trans-3-ethyl-4-methyl-2-pentene. Yes, the bond could rotate, but they use cis and trans only for drawing purposes. This tells you exactly how to place the hydrogens in the diagram. wat in the world is cis and trans? cis: hydrogens (attached to the carbons) are placed on the same side of the plane trans: hydrogens (attached to the carbons) are placed on the opposite sides of the plane
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