Chemistry: Post your doubts here!

[Lola_sweet]

You don't have to know any other product, except H2O sometimes...

Oh Thank God

the same goes for NaBH4 right? we only need to write the product

 

[asadalam]

So hows the preparation guys?Only 3 days left to the Chem P2.
What to do at this stage?Im all done with past papers and revision....

The Sarcastic Retard
qwertypoiu
Metanoia

 

[qwertypoiu]

Oh Thank God

the same goes for NaBH4 right? we only need to write the product

Yep

 

[Lola_sweet]

Yep

Thanks

 

[asadalam]

When a mixture of ethanal and propanal is reacted under the same conditions as in step I above, a similar reaction occurs with the formation of compound S, C5H10O2.

CH3CHO + CH3CH2CHO ----> C5H10O
Suggest a structural formula for S.

http://www.franklychemistry.co.uk/GCE_Papers/CIE/2009/June/9701_s09_qp_2.pdf

It's the fifth question in the second variant.

I need the structure because the answer isn't there in the mark scheme for this last part.

The ans is given in the ms:

CH3CH2CH(OH)CH2CHO
or
CH3CH(OH)CH(CH3)CHO
allow
CH3CH(OH)CH2CH2CHO

 

[qwertypoiu]

So hows the preparation guys?Only 3 days left to the Chem P2.
What to do at this stage?Im all done with past papers and revision....

The Sarcastic Retard
qwertypoiu
Metanoia

Revise over the content I guess. I'd make sure you know things like use of halogenoalkane and stuff.
But if you're truly done then sit back and relax.
I'd just make dua I guess.

 

[asadalam]

Revise over the content I guess. I'd make sure you know things like use of halogenoalkane and stuff.
But if you're truly done then sit back and relax.
I'd just make dua I guess.

BTW what are the 3 sure ways of making Halogen derivatives from

Alkenes
Alcohols

Lots are given in the book and some have conditions like heat in situ but what method should we use to make the above derivatives,that can be easily memorised

 

[The Sarcastic Retard]

So hows the preparation guys?Only 3 days left to the Chem P2.
What to do at this stage?Im all done with past papers and revision....

The Sarcastic Retard
qwertypoiu
Metanoia

Help here.

 

[The Sarcastic Retard]

We measure oxidation states in terms of each atom.

NH3
N = -3
So H3 = +3
This means that each H = +1

NH4Cl
N = -3
Cl = -1
Total charge = -4
So H4 = +4
This means that each H = +1

So the oxidation no. of H hasn't changed

So when to consider +3 in NH3?

 

[asadalam]

Help here.

How?

 

[qwertypoiu]

BTW what are the 3 sure ways of making Halogen derivatives from

Alkenes
Alcohols

Lots are given in the book and some have conditions like heat in situ but what method should we use to make the above derivatives,that can be easily memorised

From alkene:
Bubble the alkene through a concentrated solution of hydrogen halide (Eg HCl (aq)) at room temperature.
Product is a halogenoalkane.
For alcohol, it's best to learn them. I was going to suggest solid PCl5 at room temperature, but for adding bromine or iodine atom, you'd have to make them in situ. So yeah you should learn the various ways, since they may ask you about one specifically

 

[The Sarcastic Retard]

How?

Answer every possible questions asked here.

 

[asadalam]

For making halo

From alkene:
Bubble the alkene through a concentrated solution of hydrogen halide (Eg HCl (aq)) at room temperature.
Product is a halogenoalkane.
For alcohol, it's best to learn them. I was going to suggest solid PCl5 at room temperature, but for adding bromine or iodine atom, you'd have to make them in situ. So yeah you should learn the various ways, since they may ask you about one specifically

I mostly prefer SOCl as it gives more simpler products,the derivative,SO2 and H20
But Iodo and Bromo bug me.I know them but what should we generally use.

 

[nehaoscar]

So when to consider +3 in NH3?

Never really unless they ask you the oxidation number of H3 as a molecule.
Usually the oxidation numbers refer to each individual atom and not the whole molecule.
So you have to divide the charge on the molecule by the no. of atoms present to find charge on each atom and then use that charge.

 

[qwertypoiu]

I mostly prefer SOCl as it gives more simpler products,the derivative,SO2 and H20
But Iodo and Bromo bug me.I know them but what should we generally use.

I see... For them I'd say heat red phosphorus, iodine, and the alcohol together.
The phosphorus (III) iodide PI3 will be formed in situ....
Then:
3C2H5OH + PI3 ----> 3C2H5I + H3PO4.

Same with bromine.

 

[asadalam]

I see... For them I'd say heat red phosphorus, iodine, and the alcohol together.
The phosphorus (III) iodide PI3 will be formed in situ....
Then:
3C2H5OH + PI3 ----> 3C2H5I + H3PO4.

Same with bromine.

Shouldnt it be H3PO3?Look on the Oxygen atoms on both sides

 

[asadalam]

http://www.chemguide.co.uk/organicprops/alcohols/halogen.html

This is pretty good.

 

[princess Anu]

we'll name this compound as to give Cl the least number or the methyl/ethyl sidechains? what will be its name?

 

[The Sarcastic Retard]

Never really unless they ask you the oxidation number of H3 as a molecule.
Usually the oxidation numbers refer to each individual atom and not the whole molecule.
So you have to divide the charge on the molecule by the no. of atoms present to find charge on each atom and then use that charge.

Thanks a lot

 

[qwertypoiu]

Shouldnt it be H3PO3?Look on the Oxygen atoms on both sides

Yep sorry made a mistake