Presentation
Presentation on shielding and deshielded effect
- Course
- Institution
My documents contain information about chemistry it will help chemistry student a lot.
[Show more]
Seller
Follow
szshah
Content preview
Group: 5thGroup members: Sadaf Jan, Hafsa Iqbal, Habiba Zahid, Nosheen
& Aiman Shahzadi
Department: Chemistry
Semester: BS-8th
Subject: Molecular Spectroscopy
Assignment topic: Shielding and Deshielding
Submitted to: Maam Taskeen
Date: 9-May-2023
Shielding effects in NMR spectroscopy
Definition:
, Under the influence of applied magnetic field Ho, electrons surroundings nucleus
generate secondary magnetic field called induce magnetic field, which opposes
applied magnetic field in the region of nucleus. Thus the nucleus experience a
weaker magnetic field than applied magnetic field Ho and is said to be shielded .This
type of shelding is called diamagnetic shielding and its effect is termed as shielding
effect.
Explanation:
▪︎In NMR spectroscopy when the electronic density is high around the nucleus, the
opposing magnetic field of that electrons is also bigger and hence shielding is
greater.
▪︎In shielded nuclei chemical shift is observe at low frequency and up fielded.
▪︎ In shielded nuclei peak will be shifted towards right hand side in NMR spectra.
Example
Here it is possible to take into consideration the CH3 and OH proton.
1. The hydrogen atoms are shieled in CH3 and experience little applied magnetic field
and that's why required low frequency for transition and give upfield chemical shift.
In OH group hydrogen atom is deshielded because electronegative oxygen attract
electron away from hydrogen and make it deshielded. It experience applied
magnetic field and require high frequency for transition and give downfield chemical
shift.
De-shielding in NMR spectroscopy:
• Definition
When the electron density around the nuleus falls, the opposing magnetic field B 0
gets smaller, and the nucleus feels more of the external magnetic filed .
Or
The benefits of buying summaries with Stuvia:
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
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
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 szshah. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.99. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
82871 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now