100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Summary A level OCR chemistry chapter 25 notes $3.96   Add to cart

Summary

Summary A level OCR chemistry chapter 25 notes

 19 views  0 purchase
  • Course
  • Institution
  • Book

Summary in the form of questions on the left and answers on the right. Includes all the specification points for OCR.

Preview 2 out of 6  pages

  • No
  • 25
  • July 3, 2022
  • 6
  • 2021/2022
  • Summary
avatar-seller
Chapter 25

25.1- Introducing benzene
Give three properties of benzene Colourless, sweet smelling, highly flammable

Where is it found? In crude oil is a component of petrol and also found
in cigarette smoke

What is benzene classified as? Carcinogen

Draw kekule’s structure of benzene




3 ways kekule’s structure was disproven? Lack of reactivity of benzene, the lengths of the
carbon-carbon bonds in benzene, hydrogenation
enthalpies

Lack of reactivity If benzene contained C=C bonds then it would
decolourise bromine HOWEVER benzene does no
undergo electrophilic addition reactions. It does no
decolourise bromine under normal conditions. This
led scientists to suggest that benzene cannot have
any C=C bonds.

The lengths of the carbon-carbon bonds in Using a technique called X-ray diffraction, it is
benzene possible to measure bond lengths in a molecule.
When benzene was examined by Kathleen Lonsdale
it was found that all the bonds in benzene were
0.139nm in length. This bond length was between
the length of a single bond- 0.153nm and a double
bond, 0.134nm

Hydrogenation enthalpies If benzene had kekules structure, then it would be
expected to have an enthalpy change of
hydrogenation that is three times that of
cyclohexene. When cyclohexene is hydrogenated,
one double bond reacts with hydrogen. The
enthalpy change is -120KJmol-1 but as kekules
structure has 3 C=C is should be -360KJmol-1. The
actual value is -208KJmol-1

What is the current model? The delocalise model of Benzene

Benzene is a ____, ___, ____ hydrocarbon Planar, cyclic, hexagonal. 6c and 6H
containing how many carbon and how many

, Chapter 25
hydrogen atoms?

In this model how many electrons does each Each carbon atom uses three of its available four
carbon atom use up and what are they electrons in bonding to two other carbon atoms and
bonded to. to one hydrogen atom

Where is the 4th electron located? In a p-orbital at right angles to the plane of the
bonded carbon and hydrogen atoms

How do the p orbitals overlap? They overlap sideways, in both directions above
and below the plane of the carbon atoms to form a
ring of electron density.

What does this overlapping create? A system of pi bonds which spread over all six of
the carbon atoms in the ring structure

What are the 6 electrons said to be? delocalised

How do you name a benzene that has one They are shown as prefixes to benzene, eg short
substituent group? alkyl chains, halogens, nitro groups

How long does the alkyl chain have to be for 7 or more carbon atoms
benzene to become the substituent Prefix becomes phenyl
What is the prefix?

Benzoic acid


Phenylamine



Benzaldehyde 2-phenyloctane




2-chloromethylbenzene
3-chloromethylbenzene
4-chloromethylbenzene


Naphthalene


right= anthracene

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller rebeccamoore2. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for $3.96. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

79650 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling
$3.96
  • (0)
  Add to cart