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    (Original post by smith50)
    wittig mechanism

    does anyone know how to do the wittig mechanism of phosphorus ylid (phosphorane) and furfuraldehyde
    It's just going to go at the exposed aldehyde, like this, surely?
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    if 1dm^3 = 10cm*10cm*10cm (1000cm^3)
    then why doesn't 2dm^3 = 20cm*20cm*20cm (8000cm^3)??

    probably a ridiculous question, but it's really bugging me because i obviously don't understand this concept at all. ty!
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    (Original post by TRIFLUORIDES)
    if 1dm^3 = 10cm*10cm*10cm (1000cm^3)
    then why doesn't 2dm^3 = 20cm*20cm*20cm (8000cm^3)??

    probably a ridiculous question, but it's really bugging me because i obviously don't understand this concept at all. ty!
    1 dm^3 is 1 litre. 1 litre = 1000 cm^3.

    2dm^3 = 2000 cm^3

    http://en.wikipedia.org/wiki/Litre

    ^look at the first row of the table.
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    Hey can anyone help me give a good explanation why phenol, methly etc. groups act as ortho para directing groups. I really want to know the explanation and haven't found a good one as of yet...Thanks.
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    (Original post by chignesh10)
    Hey can anyone help me give a good explanation why phenol, methly etc. groups act as ortho para directing groups. I really want to know the explanation and haven't found a good one as of yet...Thanks.
    Have a look at this picture.

    Click image for larger version. 

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    Basically, the oxygen atom has two lone pairs. One of them can go towards forming a O=Arene double bond. This produces several resonance forms.

    Do you see the location of the negative charges in the resonance forms ? They are ortho and para to the phenol group.

    Hence, the electrophile (whatever it maybe) will attack at these locations of high negative charge.

    The case with a methyl group is a bit more complicated. With a methyl group we have no obvious source of electrons but what is in fact happening is that the electrons in one of the sigma C-H bonds in the methyl are overlapping with a p orbital on the C atom in the CH3 group producing a sort of weak pi bond.... From here you can see how we get the above resonance forms once more.

    Hyperconjugation is the name of this effect :

    http://en.wikipedia.org/wiki/Hyperconjugation
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    (Original post by Ari Ben Canaan)
    Have a look at this picture.

    Click image for larger version. 

Name:	Untitled 7.png 
Views:	89 
Size:	7.7 KB 
ID:	188042

    Basically, the oxygen atom has two lone pairs. One of them can go towards forming a O=Arene double bond. This produces several resonance forms.

    Do you see the location of the negative charges in the resonance forms ? They are ortho and para to the phenol group.

    Hence, the electrophile (whatever it maybe) will attack at these locations of high negative charge.

    The case with a methyl group is a bit more complicated. With a methyl group we have no obvious source of electrons but what is in fact happening is that the electrons in one of the sigma C-H bonds in the methyl are overlapping with a p orbital on the C atom in the CH3 group producing a sort of weak pi bond.... From here you can see how we get the above resonance forms once more.

    Hyperconjugation is the name of this effect :

    http://en.wikipedia.org/wiki/Hyperconjugation
    Ah ok i see, i never actually got to learn that. Thanks a lot for tr explanation! Hopefully may see you at imperial next year if i do well in the interciew!

    Is hyperconjugtion the same as sigma bond conjugation


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    (Original post by chignesh10)

    Is hyperconjugtion the same as sigma bond conjugation
    Yes
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    (Original post by chignesh10)
    Ah ok i see, i never actually got to learn that. Thanks a lot for tr explanation! Hopefully may see you at imperial next year if i do well in the interciew!

    Is hyperconjugtion the same as sigma bond conjugation


    Posted from TSR Mobile
    Yup, it sure is. In fact, I believe it is the preferred term to describe that effect.
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    Help me with this question please.When solid iron(III) oxide reacts with hydrochloric acid, iron(III) chloride solution is formed with water.
    Balanced symbol eq: 6HCL + Fe2O3 = 2FeCl3 + 3H2O

    I know iron oxide is a base so its obv a neutralisation reaction. But where in this reaction is the H+ + the OH- to give it the name of a neutralisation reaction.

    I took a guess saying the Fe initially reacts with the acid to form iron chloride solution and then it gives out hydrogen and the oxygen from the iron oxide reacts with the hydrogen in the acid to form hydroxide which then creates the neutralisation. Am I right or am I just completely wrong?
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    (Original post by Farhan96)
    Help me with this question please.When solid iron(III) oxide reacts with hydrochloric acid, iron(III) chloride solution is formed with water.
    Balanced symbol eq: 6HCL + Fe2O3 = 2FeCl3 + 3H2O

    I know iron oxide is a base so its obv a neutralisation reaction. But where in this reaction is the H+ + the OH- to give it the name of a neutralisation reaction.

    I took a guess saying the Fe initially reacts with the acid to form iron chloride solution and then it gives out hydrogen and the oxygen from the iron oxide reacts with the hydrogen in the acid to form hydroxide which then creates the neutralisation. Am I right or am I just completely wrong?
    Well, the Fe 3+ and Cl- ions are essentially spectator ions.

    Hence, the entire equation could be reduced to the general ionic equation for an acid base reaction :

    2H+ + O2- ----> H2O

    Hence, neutralisation.

    EDIT : The point I'm trying to make is that you dont necessarily have to have a H+ and OH- ion interacting to have a neutralisation reaction. A simple example would be the reaction of NH3 gas with HCl gas. You get NH4Cl.

    This is still a neutralisation reaction even though there are no OH- ions.
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    I like chemistry very much!!!!


    This was posted from my iPhone: Chat with me on Skype! Search: jj.teh
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    (Original post by Ari Ben Canaan)
    Well, the Fe 3+ and Cl- ions are essentially spectator ions.

    Hence, the entire equation could be reduced to the general ionic equation for an acid base reaction :

    2H+ + O2- ----> H2O

    Hence, neutralisation.

    EDIT : The point I'm trying to make is that you dont necessarily have to have a H+ and OH- ion interacting to have a neutralisation reaction. A simple example would be the reaction of NH3 gas with HCl gas. You get NH4Cl.

    This is still a neutralisation reaction even though there are no OH- ions.
    Thank you very much. GCSE textbooks are rather vague and dont feed you with deep understanding on most occasions.
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    I have a question in terms of Isotopes: Is it possible that Isotopes have a higher attractive force? then the centrifugal force of electrons must be weaker. That is to say that the electrons are closer to the nucleus than atoms. In other words: the atomic radius is lesser in an Isotope than in an atom. Am I right with my considerations?
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    (Original post by Kallisto)
    I have a question in terms of Isotopes: Is it possible that Isotopes have a higher attractive force? then the centrifugal force of electrons must be weaker. That is to say that the electrons are closer to the nucleus than atoms. In other words: the atomic radius is lesser in an Isotope than in an atom. Am I right with my considerations?
    Think about it carefully. What is the source of the electron-nucleus attraction? Does this change between isotopes?
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    (Original post by illusionz)
    Think about it carefully. What is the source of the electron-nucleus attraction? Does this change between isotopes?
    Let me see... the attraction force must be higher, if the nucleus has more protons than electrons on electron shell. Then the centrifugal force must be weaker. But that is not possible. Isotopes have more neutrons than protons and not vice versa. So the attraction force in an Isotope must be the same compare to an atom. That is to say the atomic radius is not lesser in an Isotope than in an atom. That's why I don't think so.

    Perhaps there are atoms which have more protons than neutrons in an nucleus?
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    (Original post by Kallisto)
    Let me see... the attraction force must be higher, if the nucleus has more protons than electrons on electron shell. Then the centrifugal force must be weaker. But that is not possible. Isotopes have more neutrons than protons and not vice versa. So the attraction force in an Isotope must be the same compare to an atom. That is to say the atomic radius is not lesser in an Isotope than in an atom. That's why I don't think so.

    Perhaps there are atoms which have more protons than neutrons in an nucleus?
    What is the charge on a neutron ?
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    (Original post by Kallisto)
    Let me see... the attraction force must be higher, if the nucleus has more protons than electrons on electron shell. Then the centrifugal force must be weaker. But that is not possible. Isotopes have more neutrons than protons and not vice versa. So the attraction force in an Isotope must be the same compare to an atom. That is to say the atomic radius is not lesser in an Isotope than in an atom. That's why I don't think so.

    Perhaps there are atoms which have more protons than neutrons in an nucleus?
    An atom always has the same number of protons and electrons. This does not change between isotopes. What does change is the number of neutrons. As the post above asks, what is the charge of a neutron? (Hint: It's in the name).

    Hence, what effect does changing the number of neutrons have on the electrostatic attraction?
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    Hey Guys, I really need some help with infra red spectra Can anyone help me ?Thanks very much guys, and happy new year and i wish everyone has a successful 2013And I love chemistry, because its more complicated than women haha
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    (Original post by D.Bman)
    Hey Guys, I really need some help with infra red spectra
    Can anyone help me ?

    Thanks very much guys, and happy new year and i wish everyone has a successful 2013

    And I love chemistry, because its more complicated than women haha
    Well, in the first one, you have the nice shoulder peaks just next to the C-H stretches at 2900 and then there's the sharp absorption at 1600. I'm guessing this is a very long chain aldehyde ?

    The second one I think is an alkene ? I'm looking at the absorption to the left of 3000 and the single peak at 1600 as proof of this. An aromatic should have multiple absorptions between 1500 and 2500.

    The third one has a nice broad peak indicating an alcohol. The sharp peak to the left might be a free OH group ?

    Fourth one..... I'm going to go all in and say this is benzaldehyde. The two small peaks to the left of 2900 are definitely due to C-H stretching of the CHO group. The 1700 peak is a C=O stretch. The low intensity peaks at around 3000 and the multiple absorption at 700-900 are definitely indicative of an aromatic ring.

    Fifth one fits the bill of a secondary amine as there is only one peak at 3400.

    The last one is definitely a Carboxylic acid; that massively broad peak centered at 3000 is the overalp of the OH and sp3 hybridised C-H stretch. Then there's the sharp peak at 1700 due to the C=O stretch of the COOH group.




    Hey, Illusionz, would you mind just quickly telling me if I'm correct ? Also, what's happening is spectra 4 ?


    (Original post by illusionz)
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    (Original post by Ari Ben Canaan)
    What is the charge on a neutron ?
    As far as I know the charge of a neutron is neutral, whereas the charge of protons is positive and the one of electrons is negative. In terms of attraction force and centrifugal force neutrons have no influence on electrons due to the charge. So I think that the changing of number has no effects on electrostatic attraction, as neutrons neither positive nor negative. That is to say that neutrons are not able to repel or to attract electrons, even if the number of neutrons is greater in an isotope. That's why electrons will not come closer to the nucleus in an isotope. From this perspective and my considerations before I'm sure that isotopes are not able to reduce the atomic radius.

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