We have just introduced four different types of isomers, which fall into two main classes. Structural isomers include linkage isomers and coordination isomers. Stereoisomers include geometric isomers and optical isomers. Structural isomers are compounds with identical molecular formulas, but different connections between the atoms. Stereoisomers are compounds with identical molecular formulas and identical connections between the atoms, but different arrangements of the atoms in space.
Linkage isomers are compounds that differ in the atom of a ligand that binds to a metal ion in a coordinate covalent bond. Coordination isomers, on the other hand, are compounds that differ only in the way the ligands and the counter-ions are distributed around the central ion. This seems confusing. Have you come up with a way to keep from confusing linkage isomers and coordination isomers?
Geometric isomers are compounds that differ only in the relative positions of some atoms. For example, trans-2-butene and cis-2-butene differ only in the positions of the CH3 groups relative to the double bond. Optical isomers differ only in the way they rotate plane-polarized light. These pairs of molecules are called chiral. Once again, the distinction between geometric isomes aand optical isomers seems confusing. Have you thought of a way to keep geometirc isomers and optical isomers straight?
In this discussion, first compare notes on the different types of isomers we have covered to make sure that everyone agrees on the different classes of isomers. Use an example if possible to help explain your answer. Then tell your classmates the ways that you have developed to determine what ype of isomer a pair of compounds represents. Also, use this as an opportunity to discuss what you find most confusing about isomers and see if your classmates have suggestions about making isomers more understandable.
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This is my understanding of isomers from the lesson.
ReplyDeleteFirst, it is important to establish what isomers are. Isomers can be defined as compounds that have the same formula but that differ in their properties.
Structural isomers are compounds with the same chemical formula but that have different connections between atoms. For example, C4 H10 O may form butanol or diethyl ether. Butanol consists of four carbon atoms connected in a chain with an oxygen atom at the end. Diethyl ether has two carbon atoms connected to one another and connected to an oxygen atom in the middle and two more carbon atoms at the end. These have different melting and boiling points.
Linkage isomers are particular structural isomers that differ in the atom of a ligand that binds to a metal ion in coordinate covalent bond. For example, NO2- forms linkage isomers.
Coordination Isomers are another type of structural isomers that differ in the way the ligand and counter-ions are arranged. For example, [Cr(NH3)5(OSO3)]Br and [Cr(NH3)5Br]SO4 are coordination isomers.
I remember structural isomers by comparing them to houses. Houses may have the same amount of square feet but they may have different lay-outs or structures.
Stereoisomers contain the same sequence of bond but different arangement of atoms in space. Cis has matching atoms side-by-side but trans has matching atoms across from one another. 2-butene is an example.
I remember this type of bond by connecting stereoisomers to "space."
Optical isomers are different in the the way they rotate plane-polarized light. Chiral means that isomers posses the property of handedness and only when atoms are different.
For example, CClBrCH3 is an optical isomer.
I remember optical by thinking of optical illusions, which trick you into looking at things different ways.
I often find it difficult to distinguish between linkage and coordination bonds. Does anyone know how to tell the difference?
The last post, the one from November 25, 2009 at 3:50 PM was Megan Dickson. Sorry, I forgot to put my name!
ReplyDeleteAndrew Park
ReplyDeleteI think I should start with stereoisomers just because they are much easier to understand than structural isomers. The two subcatergories of stereoisomers are optical isomers and geometric isomers. Stereoisomers are basically isomers that have the same molecular formula and are bonded the same way. The only difference is that they look different when they are compared three-dimensionally. (is that even a word?)
Anyway, optical isomers are just mirror images of each other. I don't know if you really need a certain technique to memorize this but I just think of optical lenses and how lenses are like mirrors and optical isomers are mirror images of each other.
Geometric isomers are isomers that have functional groups which are oriented in a different way. These two different ways are cis and trans. If a geometric isomer is considered cis, it means that a certain group is found on the same side in an isomer. If a geometric isomer is trans, it means that a certain group is found on opposite sides in an isomer. An example is 2-butene as megan has pointed out. It's easier to understand geometric isomers if you look a picture of one and read the description of it so I recommend doing that if you still do not understand my description. I don't have a way to memorize cis but I do have a way to memorize trans. A transgender changes to the opposite sex, and a geometric isomer that is a trans has a certain group that is opposite of each other.
Now for structural isomers. The two subcategories for structural isomers are the linkage isomers and the coordination isomers. Structural isomers have the same molecular formula but are just bonded in different ways.
Okay, now on to the hard stuff. If I am wrong in any of this, correct me please. Linkage isomers are isomers that differ in the connection between a central metal atom and a ligand. Before you get confused, a ligand is an atom or molecule that binds to a central metal atom. If you don't know what a central metal atom is, you're screwed (just kidding). Do you remember that there is a central atom in lewis structures? If that central atom is a metal, it is a central metal atom. Anyway, the only difference between the two isomers would be that the connection between the ligand and the central metal atom is different. [Co(NH3)5(NO2)]2+ is one example. The Co atom is the central metal atom and the NO2 is the ligand. In one isomer, the Nitrogen atom of NO2 would be the one linked to the central metal atom. In the other isomer, one of the oxygen atoms would be the one that would be linked to the central metal atom.
As for coordination isomers, they are isomers that differ in their central atoms AND certain ligands. In linkage isomers, the atoms within the ligands differed in their connection to the central metal atom. In coordination isomers, the central atom as well as certain ligands are essentially switched between the two isomers. I guess the only way to summarize this is that in linkage isomers, the atoms within the ligand are switched in their connection and in coordination isomers, the central metal atom and certain ligands are switched between the two isomers.
Andrew Park
ReplyDeleteI write too much. Anyway, Megan, your examples of the house and the optical illusions make a lot of sense. Houses are basically made from the same materials (most of them) but they differ in their shape. The optical illusion one is good too because in optical isomers, we see double, except that one of the isomers is reversed. You should read about my description of linkage isomers and coordination isomers. It may or may not help (if you ever read this). haha
Josh Dos Santos
ReplyDeleteI just typed for an hour and when I clicked post, edline told me I had been inactive for too long and I lost EVERYTHING. ugh
anyways, I will just be extremely concise in what I will say. I went way more in depth before.
In structural isomers, the differences are in CONNECTIONS.
**There is nothing about 3d, it is 2d. It has nothing to do with angles, arrangement, or symmetry.
It is like a jigsaw puzzle.
In Butanol and Diethyl ehter, the CONNECTIONS ARE DIFFERENT.
LINKAGE ISOMERS: differ in atom of LIGAND that binds to metal ion in COORDINATE COVALENT BOND.
(found in COORDINATION COMPLEXES, made of metal cations and ligands, or electron rich ions or molecules.)
Now linkage isomers are those in which the differences in connection occur inside the brackets [] without the counterion.
i.e. [Co(NH3)5(NO2)]Cl2, the difference is in how the NO2 binds to the molecule inside the brackets.
either by N or by O.
You are ROTATING a piece of the puzzle.
In COORDINATION isomers are those in which the ligands AND counterions are distributed differently.
This deals with ions outside the brackets and inside.
You replace an ion inside with the counterion like in ...
[Co(NH3)4Cl2]Br**notice Br is at end
[Co(NH3)4ClBr]Cl**notice Br and one Cl switched.
You are switching a piece of the puzzle with a piece you had placed aside.
STEREOISOMERS deals with ARRANGEMENT not connection.
It deals with geometric terms like OPPOSITE or ADJACENT such as in [Co(NH3)4Cl2]Br
where the difference is in if Cl is opposite or adjacent to the other Cl.
GEOMETRIC isomers have to do with symmetry.
It is like the molecule is on a sheet of paper and you fold it so that two ions are OPPOSITE each other or ADJACENT to each other.
they can have a glide-reflection symmetry as in 2 Butene when the CH3 are opposite each other across the double bonded carbons.
Or they can be ADJACENT.
lastly, Optical isomers are mirror images.
These are like legos. It has to do with whether an ion is coming towards you or away from you.
lets take 1chlorobutanol.
the differences is whether the OH and Cl are coming out of the plane or going into it.
Say you have a lego castle with bridges going to lego posts.
some posts are aligned with the castle..
x===O====x
some are going away from the castle and some are coming from it.
y
^
O
v
x
In optical isomers, the x and y switch. You picked up one lego post and switched it with the other one.
The lego castles are the same except that those lego posts are now facing a different direction than they were. No different connections, just direction and arrangement.
Megan,
ReplyDeleteI think that Linkage only deals with the molecule inside the brackets while coordination deals with a switch between the counterion and the ligand.
In linkage, a puzzle piece is rotated so that a different part of that piece connects to the puzzle.
In coordination, you switch a piece with another that you had off to the side.
Josh Dos Santos
Andy,
ReplyDeletehahhaha I love your way of remembering trans with transgender!! It really helps.
Maybe for cis you can think sis, like sister.
So maybe the ions are close sisters and are adjacent.
Josh Dos Santos
Allie VanO
ReplyDeleteAgh, so long.
Start with Stereoisomers which basically contains the same functional groups but they vary in their atom arrangement in space.
Sub categories of steroisomers include the geometric isomers and the optical isomers.
Geometric Isomers vary in their spatial position around bonds with restricted movements. The two types are cis and trans with trans crossing over to the other side and cis merely being on the same side of the molecule or compound.
Think of trans like tranverse which means crossways or crossing over to the other side.
I think of geometric isomers in forms of geometry thinking of the switches or change in arrangement as angles or something like that.
As for optical isomers basically these follow a mirror image pattern within the functional groups. When I think of optics I think of the whole thing with the human eye where the eye perceives the world upside down and then it's reversed to make things right side up. Except when you look into the inverted side of a spoon and it's upside down again..but I'm getting ahead of myself.
Structural isomers are where the atoms and functional groups are joined differently basically involving changes with the bonds. There are linkage isomers and coordination isomers.
Linkage isomers basically differe in the atom of the ligand that binds the metal ion in a coordination covalent bond. Basically it involves the link between the atoms.
Coordination isomers differ when it comes to the placement of counter ions which switch places with ligands. I look at this as the coordinating where the counter ion goes.
Allie-Vano.
ReplyDeleteAh, you guys make me laugh sometimes, with your transgender examples and what not.
My only problem with the optical illusion idea is the fact that optical illusions involve tricking the eye into seeing something thats not there or is hidden which really doesn't involve the whole mirror idea unless we're talking about funhouse mirrors.
I guess you can also look at a stereoisomer as magnetix, if you have ever played with those basically you have your link magnets and these metal orbs that serve as the center where you can join the link magnets. It's pretty fun actually and serves as a good example for how you can switch the links around to make different shapes but you still have the same bonds and number of atoms.
Megan Dickson
ReplyDeleteAndy,you gave a very good description of linkage and coordination isomers were very helpful. I was struggling a little bit to understand what a ligand was, but you cleared that up. Thank you! Sometime the vocabulary involved in identfiying isomers can be confusing for me. I understand now the metal ion that a ligand connects with is simply the ion in the center of a lewis structure that is a metal.
Moon Kyu Kim
ReplyDeleteI'm pretty late because I didn't know that we had homework during the thanksgiving. I read all comments above me and I strongly agree with Andrew's definition. He clearly defined all isomers, however, I want to define it in my own words. So...
I want to go in order. So, I will do the linkage isomer fisrt. It is the isomer which
differs with which element the central atom has the coordinate bond. For example, there is a central C atom and it has NO2 as a ligand. Then C may have coordinate bond with N or O.
It is the only difference in linkage isomer.
Second, for coordination isomer, it is pretty easy because only one of the ligand and counter atoms are rotated in two isomers. For example we have Centeral carbon atom and we have 2 chloride atoms around it and 1 bromine as counter atom. Then, in coordination isomer, bromine and chloride can be switched.
Then, I'll go for stereoisomer.
For optical isomer, it is the mirror image of another isomer. In the three dimentional feature, atomes can go back and forth depeding on its structure. Then, which goes back and which goes forward? this is the most important thing about the optical isomer.
For geometric isomer, we use the term "cis" and "tran" to describe which is which. When two same ligands are on the same side, so it is same when it is flipped, we call this "cis"
When two same ligands are opposite side, so it is different in shape when we flip it, it is called "trans" I think the video well explained about "cis" and "trans" and I learned about flipping thing from my previous school;; So, fix me if I have some wrong ideas.
Ellen Cho
ReplyDeleteFirst, structural isomers have same formulas but atoms are bonded differently. Linkage isomers and coordination isomers are included in structural isomers. Linkage isomers are isomers that have the same composition but metal and ligand are connected differently. Ligand is made up of a metal cation and electron-rich ions or molecules. For example, CN- is one of linkage isomers. the coordination isomers are isomers that have different structures of the ligands and counter-ions around the central metal ion. for example,[Cr(NH3)5(SO4)]Br and [Cr(NH3)5Br]SO4 have both Cr as the central metal ion and 5 of NH3, SO4 and Br are distributed aroun Cr. In the first one, Br is counter-ion, but in the secont one, SO4 is the counter-ion. Like this, both have a formula of Cr(NH3)5SO4Br, but the distribution of ions are different that they are called the coordination isomers.
Second, Stereo isomers are isomers that have different arrangements atoms in space. Geometric isomers and optical isomers are included. Geometric isomers have same formula and bonds, but atoms are in different positions. Optical isomers differ in way they rotate plane-polarized light that they look like reflected in the mirror. When they rotate light to right, it's called dextrorotatory and when they rotate light to left, it's called levorotatory. I think they are much easier to understande than structural isomers since their name tells almost everything what they are about.
Ellen Cho
ReplyDeleteI read all others' comments and I think I can understand more than what I did before since everyone explained in different words and I could learn in many other ways.
I think it was great idea to remember structural isomers by comparing them to houses because houses have all different structures. I think will help me to memorize about structural isomers better.
Dang.... Everyone wrote so early and so long..... This is frightening me so much XD
ReplyDeleteAnyway, the slacker will get down with this thing and just summarize what others have already said.
I'll start off with talking about different types of isomers.
First off, there is Geometric Isomers. Geometric Isomer is composed of two different types: Cis and Trans. Cis type of isomers have a same functional group on the same side of the molecule. On the other hand, the trans isomers have a same functional group on the opposite side of the molecule.
Also, there are isomers called structural isomers. These isomers have difference in their intra-molecular bonding. Even though consisted with same number of elements (which implies that their molecular formula is the same), there way of bonding differs if the molecules are isomers. If I am understanding correctly, these isomers have different arrangements of atoms.
Linkage Isomers founds its difference in the central atom and the ligand. I am not sure if the central atom has to be metal atom, though.
Due to my lack of understanding, i can not elaborate more on the linkage Isomers.
And finally, there is an isomer called optical isomer. Optical isomer is easy to understand since that it is same as the relationship of the mirror. The isomer molecules of this kind is exact opposite of each other, like facing the mirror.
This is the things that i understood so far, but it might be wrong. So feel free to correct my wrong knowledge that i have falsely obtained... Anyway, moving on with the prompt, i have quite few problems understanding the isomers. Even though all the isomers is supposed to be different...
Why do they look all the same to me?
I understand that the physicality of the molecules actually affect the workings of the molecule, and that because of such property, the isomers are categorized differently. However, the problem is that their way of categorization seems all the same.
Can anybody enlighten me with sparkling light of knowledge?
Even thought i wrote my definition of isomers on this answer, my lack of confidence keeps questioning its truthfulness...
I'll be waitin for you guys' brilliant answers...
Oh, by the way, Can you explain structural isomers for me, josh? When you say it only applies to 2 dimensions, does it mean that the only planar molecules have structural isomers? I mean, doesn't most of the molecules form a 3 dimensional structure? If it does not apply to 3 dimensional molecules, wouldn't there be small amount of structural isomers, making it hard for other molecule to categorize according to the idea of structural isomers?
ReplyDeleteJust a bit confused..... plz enlighten me XD
Dwayne Hahm
ReplyDeleteThis lesson was hard to understand and was very confusing
It is the main thing to define the isomers. Isomers can be defined as compounds that have the same formula but that differ in their possessions.
I remind myself of structural isomers with the cars, like Accord, Camry, Mazda 6, and Five Hundred have the same performance, but just the companies are different.
Structural isomers have the exactly same chemical formula and just have different structures among atoms. For example, C4 H10 O can be butanol or diethyl. The reason is butanol has the oxygen atom at the end, but diethyl has two more carbon atoms at the end. These different structures also make different characteristics, such as boiling point. Linkage isomers are called particular structural isomers, because it has different in the atom of a ligand that binds to a metal ion in coordinate covalent bond. For example, NO2- forms linkage isomers. Coordination Isomers are an additional form of structural isomers that differ in the way the ligand and counter-ions are arranged. For example, [Cr(NH3)5Br]SO4 and [Cr(NH3)5(OSO3)]Br. Stereoisomers have the same series of bond, but different atoms’ arrangement. Cis has matching atoms side-by-side but trans has matching atoms across from one another. For example, 2-butene. I just make a 3 dimension space on my head and think about it. Optical isomers are different in the way they rotate plane-polarized light and Chiral means isomers group the property of handedness. For example, CClBrCH3. I find similarity of optical with the persons’ face as it looks different in any angles.
All the people had their own fancy way to interpret the isomers easily. It was really hard for me to differentiate the isomers, but as I got the ideas from my good fellows, I feel like I can understand more vividly.
ReplyDeleteDwayne Hahm