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Edexcel Chemistry Unit 5 June 19 2012

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Can someone explain this to me? Jan 2011, Q7:

Which of these will NOT form an amide with ethanoyl chloride:

A: NH3
B: CH3CH2NH2
C: CH3CH2NH(CH3)
D: CH3CH2N(CH3)2

Correct answer is meant to be D.
I know NH3 + acid chloride >>> amide, so it can't be A, but why is it D out of B, C and D?

Reply 301

TheDawn

Whats the oxidation state of Co in this complex ??

[CO(NH3)4CL2]CL ??

Reply 302

arnab

Original post by Arusa01

Basically

Deprotonation = Think of it this way you have your ligand of say [Fe(h20)6]3+. Now when in contact with water the lone pairs on water is strong enough to actually pull a hydrogen off the water in the ionic complex. so [Fe(h20)6]3+ + h20 --> [Fe(h20)5(OH)]2+ + h30+. As you can see the iron complex has lost a hydrogen (hence there now being (h20)5(OH) and also the charge on the overall complex has gone down by one as a H+ ion has left).

Ligand reaction : This is just when one ligand can kick another one out, like a substitution reaction. Some ligands are stronger than others, just like metals in the reactivity series. Water is a very weak ligand when compared with ammonia or cyanide ions, so if put ina solution of these the cyanide ions or ammonia will replace the water in the complex.

Simple example.

[Fe(h2O)6]2+ + 6CN- --> [Fe(CN)6]4- + 6H2O.

Note that the Cyanide ions have replaced the water ones. Also the charge is easily determined, it is just the charge of 6 CN- ions and the charge of a Fe2+ ion. So it will be -6 +2= -4. Hence the charge of the new complex!

ahhh thanks! So bascally Deprotonation is when a complex ion loses a proton and a losses its charge?

Reply 303

arnab

Original post by Arusa01

hey can you also explain to me amphoteric behaviour? still confused on that :s-smilie:

Reply 304

xxbiologyxx

may i know if cyclohexene contains a delocalised ring?i know benzene has one but not for cyclohexane.so how about cyclohexene?!! HELP URGENT! thanks! :smile:

Reply 305

arnab

Original post by xxbiologyxx

may i know if cyclohexene contains a delocalised ring?i know benzene has one but not for cyclohexane.so how about cyclohexene?!! HELP URGENT! thanks! :smile:

short answer, no

Long answer : http://en.wikipedia.org/wiki/Cyclohexene :tongue:

Reply 306

xxbiologyxx

Original post by arnab

short answer, no

Long answer : http://en.wikipedia.org/wiki/Cyclohexene :tongue:

thanks! but right, in Sample Assessment Material, Qs 21c. Comment critically on the differences and similarities of the first steps involving......
According to the mark scheme, it says both (benzene and cyclohexene) are attacked by electrophiles DUE TO STABILITY OF DELOCALISED RING.does that mean cyclohexene have a delocalised ring as well? O_O

Reply 307

skylight17

Original post by xxbiologyxx

That's Unit 4 not Unit 5

Reply 308

xxbiologyxx

Original post by skylight17

That's Unit 4 not Unit 5

huh NO!

it's in unit 5 SAM. i'm working on it right now.am so frustrated and confused. :confused:

can anyone shed some light on it? thank you! :tongue:

Reply 309

aqua05

hey guys can someone tell me what stuff are we suppose to know for transition metals..
Just summarise for me the sub topics no need for explanation..just want to make sure i have done everything :smile:

thanks

Reply 310

This Honest

Original post by xxbiologyxx

huh NO!

it's in unit 5 SAM. i'm working on it right now.am so frustrated and confused. :confused:

can anyone shed some light on it? thank you! :tongue:

Cyclohexene has 1 double bond so it can undergo electrophillic addition with Br2. It hasn't got a delocalised ring

Reply 311

aqua05

Original post by giraffegiraffe

hii

Well.. during the formation of an amide..usually H(joined to N) is lost..
So for B
CH3CH2NH2 + ethanoyl chloride ---> CH3CH2NHCOCH3 + HCl
for C
CH3CH2NH(CH3) + ethanoyl chloride ---> CH3CH2N(CH3)COCH3 + HCl

The last reaction cannot take place.. coz according to the reactions ethanoyl chloride(acyl chloride) must remove HCl as their biproduct.

Reply 312

xxbiologyxx

Original post by This Honest

Cyclohexene has 1 double bond so it can undergo electrophillic addition with Br2. It hasn't got a delocalised ring

Uhh! so the stabilised ring here refers to benzene?! ugh!now i got it thanks! :smile:

Reply 313

indiankid1

Okay so, you know when you've done your titrations, how many cm3 should your titres be different from each other? Is it within 0.2 cm3 of each other? Or 0.1?

This was posted from The Student Room's iPhone/iPad App

Reply 314

Teabo

Original post by TheDawn

Whats the oxidation state of Co in this complex ??

[CO(NH3)4CL2]CL ??

Okay, in this, NH3 as you know, is neutral. There are 3 Cl atoms present, they will always have a -1 charge in transition metal complexes. So, total of -3, and since the overall charge on this formula, is neutral, the Cobalt ion must balance it, and will thus be Co+3.

Reply 315

im so fresh

Someone explain question 9 of the multiple choice on the june 2010 paper.

how did they get the ratio?

Reply 316

Kasarna

Original post by nmudz_009

Thanks. In my book it only shows the reaction equations of aqueous sodium hydroxide and aqueous ammonia. Where can I find the reactions of the rest of them, or is there any way to work them out? :frown:

Yeah NaOH and NH3 are the only deprotonation reactions we need to know. *Though you also need to be aware that hydrated Cu2+ ions can be deprotonated by amines and then eventually have a ligand exchange happening.* If you have the George Facer book Pge. 225

As for the negative ligands, my book gives no examples of reactions and only mentions as examples there may be other ligands and then it lists them along with the name you would use.

Reply 317

Kasarna

Original post by im so fresh

Someone explain question 9 of the multiple choice on the june 2010 paper.

how did they get the ratio?

I'll explain Q9 and you can help me with Q5 since I just don't understand it?

Anyway Q9;

Cr in dichromate has an oxidation state of +6 and is reduced to +3. So therefore 3 electrons are needed. However there are 2 Cr 6+ ions in dichromate therefore 6 electrons are needed.

Am sure you know that when Fe2+ is oxidised one electron is lost so therefore you would need 6 moles of Fe2+ ions to provided the needed 6 electrons.

Reply 318

marcus94

Original post by Kasarna

I'll explain Q9 and you can help me with Q5 since I just don't understand it?

Basically, transition metals lose their s electrons first so there is a large jump from 2-3 and the jump from 7-8 shows that it has an electron in the d-subshell(5 in this case)

Also - Does anyone have the sample paper?

(edited 11 years ago)

Reply 319

im so fresh

Original post by marcus94

You need to find out the half equations to both and then balance it to give an overall equation.. off the top of my head without looking at data sheets i think its 5:1 because dichromate get reduced, there are 5e- and iron oxidised has 1e-

Also - Does anyone have the sample paper?