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OCR F324-June 2013 Chemistry

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- The c=c bonds in Kekule structure do not react the same way as in alkenes. It does not take part in electrophilic addition.
- Kekule also suggested c=c and c-c bonds, however x-ray determined that all bonds had the same legths in bezene as apposed to dieferrent lengths from c=c and c-c bonds.
- Kekules' structure is also less stable than the real benzene structure.

yes correct!

Reply 481

MasterYi

Original post by otrivine

yes correct!

Define retention time.
And briefly describe the steps in gas chromotography.

Reply 482

otrivine

Original post by MasterYi

Define retention time.
And briefly describe the steps in gas chromotography.

have not revised that yet

Reply 483

MasterYi

Original post by otrivine

have not revised that yet

Ok, explain why phenol can be brominated easier than Benzene. [3 marks]

Reply 484

otrivine

Original post by MasterYi

Ok, explain why phenol can be brominated easier than Benzene. [3 marks]

Phenol has an OH group in which the oxygen has a lone pair of electron and is drawn into the ring. This creates a region of high electron density and as a result, the ring becomes activated. Because of this the bromine Br-Br bond becomes polarised easily and is attracted towards the ring because of the rich electron density.

Reply 485

MasterYi

Original post by otrivine

Yes correct. Its alo kinda hard to revise this module because it involves a lot of looking/drawing molecules and analysing stuff.

Reply 486

otrivine

Original post by MasterYi

Yes correct. Its alo kinda hard to revise this module because it involves a lot of looking/drawing molecules and analysing stuff.

Yes, but there are lots of definitions and describing in chapter 1!

Define:carbon neutral

Define:amphoteric

Reply 487

MasterYi

Original post by otrivine

Yes, but there are lots of definitions and describing in chapter 1!

Define:carbon neutral

Define:amphoteric

Carbon neutral: something thats produces the same amount of carbon that it takes in.

Amphoteric: A molecule which has the characteristics of both an acid and base.

Reply 488

otrivine

Original post by MasterYi

Carbon neutral: something thats produces the same amount of carbon that it takes in.

Amphoteric: A molecule which has the characteristics of both an acid and base.

first one, you wont get the mark if you say that in the exam, it should be that , its where a crop releases the same amount of co2 and the same amount of co2 is absorbed when combusted.

second one is perfect!

my turn :smile:

give me challenging one

Reply 489

MasterYi

Original post by otrivine

give me challenging one

Okay.

1,4-diaminobenzene can irrate the skin because it is basic. Therefore, it is sometimes neutralised with EXCESS HCL acid to give the salt.

Explain how the amino groups in a primary amine such as the one I mentioned allow the molecule to act as a base. [2 Marks]

Reply 490

otrivine

Original post by MasterYi

The nitrogen present in 1,4-diaminobenzene is a base and accepts a proton. Therefore, This results in both sides of -NH2- to form NH3 ⁺

Reply 491

MasterYi

Original post by otrivine

The nitrogen present in 1,4-diaminobenzene is a base and accepts a proton. Therefore, This results in both sides of -NH2- to form NH3 ⁺

Okay, correct. That wasn't hard enough.

Reply 492

otrivine

Original post by MasterYi

Okay, correct. That wasn't hard enough.

was this meant to be hard?

How do you make nitrous acid (3)

Reply 493

MasterYi

Original post by otrivine

was this meant to be hard?

How do you make nitrous acid (3)

No, i couldn't find any. :frown:

NaNO₂ + HCl --> HNO₂+ NaCl

This will be last one for today, I'm sleeping.

Explain why triglycerides are soluble in non-polar solvents ut not in water.

Reply 494

otrivine

Original post by MasterYi

No, i couldn't find any. :frown:

NaNO₂ + HCl --> HNO₂+ NaCl

This will be last one for today, I'm sleeping.

Explain why triglycerides are soluble in non-polar solvents ut not in water.

Yes, and also mention the reaction mixture takes place in in-situ

Because triglycerides form long chains of carbon ,hydrogen and oxygen and therefore is not soluble in water. The reason for this is because there is no hydrogen bond formation between the triglyceride and water molecule due to triglyceride not containing any hydroxyl groups (-O-H-) and therefore not soluble.