This presentation describes the concept of Hyperconjugation in simple words, gives definition of hyperconjugation, explains why it is called as 'No bond Resonance' and gives the effects of hyperconjugation on the chemical properties of compounds: alkyl cations and their relative stability, alkyl radicals and their relative stability, alkenes and their relative stability, bond length, anomeric effect and Baker - Nathan effect.
An organic species which has a carbon atom bearing only six electrons in its outermost shell and has a positive charge is called carbocation.
The positively charged carbon of carbocation is sp2 hybridized.
The unhybridized p-orbital remains vacant.
They are highly reactive and act as reaction intermediate.
They are also called carbonium ion.
An organic species which has a carbon atom bearing only six electrons in its outermost shell and has a positive charge is called carbocation.
The positively charged carbon of carbocation is sp2 hybridized.
The unhybridized p-orbital remains vacant.
They are highly reactive and act as reaction intermediate.
They are also called carbonium ion.
This is a presentation file on Inductive Effect, Bond Length, Bond Energy, Bond Angle for the course Organic Pharmacy I, course code is PHAR-1105 specially for the pharmacy students. Also it can be used for the Biochemistry students and other like as HSC level in Bangladesh or another country. We are the students of Mawlana Bhashani Science and Technology University, department of pharmacy which is located in Tangail.
Thank you for your patient.
The delocalization of σ-electron in to adjacent π orbital or p-orbital is called hyperconjugation. The contributing structures involving sigma electrons of C - H bond do not show any covalent bond between C and H. Hyperconjugation, therefore, is also called as "no bond resonance" or "Baker-Nathan effect
Hyperconjugation is the donation of a sigma bond into an adjacent empty or partially filled p orbital, which results in an increased stability of the molecule.
Contributed by: Samuel Redstone (Undergraduate), University of Utah, 2016
Cyclohexane exists in different conformations viz chair, boat, twist boat and half chair. These conformations possess different energies. Therefore they differ in energy.
This is Power Point Presentation on Topic "Electrophilic Aromatic Substitution Reactions" as per syllabus of "University of Mumbai" for S.Y. B. Pharmacy (Sem.: IV) students.
This is a presentation file on Inductive Effect, Bond Length, Bond Energy, Bond Angle for the course Organic Pharmacy I, course code is PHAR-1105 specially for the pharmacy students. Also it can be used for the Biochemistry students and other like as HSC level in Bangladesh or another country. We are the students of Mawlana Bhashani Science and Technology University, department of pharmacy which is located in Tangail.
Thank you for your patient.
The delocalization of σ-electron in to adjacent π orbital or p-orbital is called hyperconjugation. The contributing structures involving sigma electrons of C - H bond do not show any covalent bond between C and H. Hyperconjugation, therefore, is also called as "no bond resonance" or "Baker-Nathan effect
Hyperconjugation is the donation of a sigma bond into an adjacent empty or partially filled p orbital, which results in an increased stability of the molecule.
Contributed by: Samuel Redstone (Undergraduate), University of Utah, 2016
Cyclohexane exists in different conformations viz chair, boat, twist boat and half chair. These conformations possess different energies. Therefore they differ in energy.
This is Power Point Presentation on Topic "Electrophilic Aromatic Substitution Reactions" as per syllabus of "University of Mumbai" for S.Y. B. Pharmacy (Sem.: IV) students.
This presentaion describes about the basic principle effects in organic chemistry like inductive,mesomeric,electromeric, resonance and hyperconjugation. this presentation contains some JAM competitive questions.
Carbocations and factors affecting their stabilitykoskal
A carbocation is a species where a carbon atom bonds to three carbon atoms and has a positive charge. Carbocations are electron deficient species and therefore very reactive and unstable. Anything which donates electron density to the electron-deficient center will help to stabilize them.
Stereo chemistry of substitute cyclohexane presentationMUKULsethi5
this video very useful for all chemistry related exam like
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in this we discuss stereochemistry of substitute cyclohexane.
we discuss about
1,3 diaxal interaction
1,2 interaction
mono substitute cyclohexane
Conformation of Cyclohexane
Stereochemical configuration of cyclohexane
Newman projection of cyclohexane
Repulsion energy of substituent in cyclohexane
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June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
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Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
2. Resonance involves delocalization of π electrons, leaving
the σ bond untouched.
However in some cases, a σ bond and an adjacent π bond
may get involved in resonance.
Such a delocalization is called as Hyperconjugation.
3. •Stabilizing effect of the
molecule
•Interaction of sigma (σ) bond
(eg. C – H, C – C) with a pi
(π) network.
4. When carbon possessing atleast one Hydrogen is attached
to another carbon bearing an unshared orbital or to an
unsaturated carbon, there are more than one structure
(canonical forms) possible for the molecule.
These result from the overlap of the bonding electrons of
C – H σ bond with 2p or π orbital of the adjacent carbon
atom.
As a result, the bond between carbon and hydrogen does
not exist anymore.
5. The shared pair of electrons is now borne by carbon alone and
hydrogen is in its close proximity as proton.
The negative charge developed on the carbon gets delocalized
by overlap with adjacent p orbital.
6. Hyperconjugation: No bond resonance
The electrons of the sigma bond between C and H are involved in delocalization.
In structure to the right: No bond between C and H due to migration of the sigma bond.
Hence Hyperconjugation is also called as ‘NO BOND RESONANCE’.
This does not indicate that hydrogen is completely detached from the structure, but some
degree of ionic character in the C – H bond and some single bond character between
carbon – carbon double bond.
7. Such an interaction is also referred to as ‘Heterovalent’ or ‘Sacrificial
hyperconjugation’.
This is so named because the contributing structure contains one two-electron bond less
than the normal Lewis formula of the compound.
At present, there is no evidence of sacrificial hyperconjugation with neutral
hydrocarbons
9. Alkyl cations and their relative stability
Carbocations have an electron deficient (positively charged) carbon.
The empty p orbital of this sp2 carbon can overlap with σ orbital of C – H bond of
adjacent alkyl group (α C – H bond).
This overlap permits individual electrons to help bind together three nucleus: 2 carbon and
1 hydrogen.
The positive charge thus gets dispersed over large volume of space and is stabilized.
10. The more the number of alkyl groups on the carbocation, more is the number of α C – H σ
bonds and hence more are the possibilities for hyperconjugation which makes the carbocation
more stable.
The order of stability of the Carbocations is:
30alkyl carbocation > 20alkyl carbocation > 10alkyl carbocation > methyl carbocation
9
Hyperconjugable
H
6
Hyperconjugable
H
3
Hyperconjugable
H
No
Hyperconjugable
H
11. Alkyl radicals and their relative stability:
Alkyl radicals have p-orbital of carbon occupied by an odd electron which gets
delocalized over three nuclei (2 carbon and 1 hydrogen) by the overlap with the σ
orbital of C – H bond of adjacent alkyl groups.
The bond is formed between 2 carbons and odd electron is held by the hydrogen atom.
12. The order of stability depends on the
extent of delocalization. The greater the
delocalization, the more is the stability.
30alkyl radical > 20alkyl radical > 10alkyl
radical > methyl radical
13. Alkenes and their stability
Overlap of σ orbital of C – H bond with π orbital of adjacent C – C
double bond gives rise to canonical structures.
Delocalization of electrons occurs over three nuclei and thus stabilizes
the alkene.
14. α C – H possesses partial ionic character and its electrons get delocalized
into the adjacent π system.
More the substituent, more is the opportunity for hyperconjugation and
more stable is the alkene.
15. Stability of alkenes will increase with increase in number of Hydrogen α to unsaturated system.
Increasing order of stability of alkenes because of Hyperconjugation:
Alkene Number of Hyperconjugable Hydrogen
(α to unsaturated function)
CH2=CH2 0
(CH3)CH=CH2 3
(CH3)2C=CH2 (CH3)CH=CH(CH3) 6
(CH3)2C=CH(CH3) 9
(CH3)2C=C(CH3)2 12
16. Bond length
Hyperconjugation leads to shortening of sigma (σ) bond.
Eg. C – C bond in 1,3-butadiene and methylacetylene is 1.46 A0 in
length, much less as compared to 1.54 A0 found in saturated
hydrocarbons.
For butadiene, this can be explained by the normal conjugation of 2
alkenyl parts. But for methylacetylene, hyperconjugation between
alkyl and alkynyl parts.
17. Anomeric effect
The general tendency of anomeric substituents to prefer an axial orientation is called as
anomeric effect.
α-methyl glucoside is more stable than β-methyl glucoside due to hyperconjugation.
In β-methyl glucoside the methoxy group is at equatorial position and cannot involve in
hyperconjugation. Therefore β-methyl glucoside is less stable than the α-methyl glucoside.
α-methyl glucoside Β-methyl glucoside
18. Baker – Nathan Effect
Alkyl groups are electron donating. The relative magnitude of this
inductive effect of alkyl groups is:
30 > 20 > 10 > CH3
This order is reversed when an alkyl group is directly attached to an
unsaturated system, where the electron release is maximum for CH3 & the
order is:
CH3 > 10 > 20 > 30
19. This is known as a Baker – Nathan effect and was explained
by John W. Baker and W. S. Nathan on the basis of
Hyperconjugation.
20. In –CH3 there are 3 hyperconjugable hydrogen atoms, thus more
stabilization by hyperconjugation.
In –CH2CH3 there are only 2
In –CHR there is only 1.
This explains the reversal of order where electron release is not by
inductive effect but by Hyperconjugation.