1) Nucleophilic substitution reactions involve the attack of a nucleophile on an alkyl halide, replacing the halide leaving group.
2) SN1 reactions are unimolecular nucleophilic substitutions that proceed through a carbocation intermediate. The rate depends only on the concentration of the alkyl halide.
3) Tertiary alkyl halides typically undergo SN1 reactions since the tertiary carbocation intermediate is most stable. This can lead to partial or full racemization of chiral reactants.
The haloalkanes are a group of chemical compounds derived from alkanes containing one or more halogens. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially and, consequently, are known under many chemical and commercial names.
B.Pharm I Year II Sem. SN1 and SN2 reactions, kinetics, order of reactivity of alkyl halides, stereochemistry and rearrangement of carbocations.
SN1 versus SN2 reactions, Factors affecting SN1 and SN2 reactions.
Structure and uses of ethylchloride, Chloroform, trichloroethylene, tetrachloroethylene,
dichloromethane, tetrachloromethane and iodoform.
Alcohols, Qualitative tests for Alcohol, Structure and uses of Ethyl alcohol, chlorobutanol, Cetosterylalcohol, Benzyl alcohol, Glycerol, Propylene glycol
Nucleophilic Substitution reaction (SN1 reaction)PRUTHVIRAJ K
Attack of nucleophile at a saturated carbon atom bearing substituent, known as leaving group results in Substitution reaction.
The group that is displaced (leaving group) carries its bonding electrons.
The new bond is formed between nucleophile and the carbon using the electrons supplied by the nucleophilic agent.
The compound on which substitution takes place is called “substrate.”
The substrate consists of two parts, alkyl group and leaving group.
The haloalkanes are a group of chemical compounds derived from alkanes containing one or more halogens. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially and, consequently, are known under many chemical and commercial names.
B.Pharm I Year II Sem. SN1 and SN2 reactions, kinetics, order of reactivity of alkyl halides, stereochemistry and rearrangement of carbocations.
SN1 versus SN2 reactions, Factors affecting SN1 and SN2 reactions.
Structure and uses of ethylchloride, Chloroform, trichloroethylene, tetrachloroethylene,
dichloromethane, tetrachloromethane and iodoform.
Alcohols, Qualitative tests for Alcohol, Structure and uses of Ethyl alcohol, chlorobutanol, Cetosterylalcohol, Benzyl alcohol, Glycerol, Propylene glycol
Nucleophilic Substitution reaction (SN1 reaction)PRUTHVIRAJ K
Attack of nucleophile at a saturated carbon atom bearing substituent, known as leaving group results in Substitution reaction.
The group that is displaced (leaving group) carries its bonding electrons.
The new bond is formed between nucleophile and the carbon using the electrons supplied by the nucleophilic agent.
The compound on which substitution takes place is called “substrate.”
The substrate consists of two parts, alkyl group and leaving group.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Ethnobotany and Ethnopharmacology:
Ethnobotany in herbal drug evaluation,
Impact of Ethnobotany in traditional medicine,
New development in herbals,
Bio-prospecting tools for drug discovery,
Role of Ethnopharmacology in drug evaluation,
Reverse Pharmacology.
This is a presentation by Dada Robert in a Your Skill Boost masterclass organised by the Excellence Foundation for South Sudan (EFSS) on Saturday, the 25th and Sunday, the 26th of May 2024.
He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
How to Split Bills in the Odoo 17 POS ModuleCeline George
Bills have a main role in point of sale procedure. It will help to track sales, handling payments and giving receipts to customers. Bill splitting also has an important role in POS. For example, If some friends come together for dinner and if they want to divide the bill then it is possible by POS bill splitting. This slide will show how to split bills in odoo 17 POS.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
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.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
2. ALKYL HALIDES
Alkyl halides are organic molecules containing a halogen atom bonded to
a sp3 hybridised carbon.
C X
sp3 hybridised carbon
X= F, Cl, Br, I
Alkyl halide Alkyl halides classification
3. SUBSTITUTION REACTION
The carbon-halogen bond in alkyl halides is polar because of the
high electronegativity of the halogen atom relative to carbon.
The carbon atom is therefore a good target for attack by nucleophiles
(electron rich species).
In fact, the nucleophilic substitution reactions are the most common
reactions of alkyl halides.
Nucleophile Alkyl halide Substitution product Leaving group
4. WHAT IS NUCLEOPHILIC SUBSTITUTION
REACTION ?
When a substitution reaction involves the attack by a nucleophile,
the reaction is referred to as SN (S stands for substitution and N for a
nucleophile).
The hydrolysis of alkyl halides by aqueous NaOH is an example of
nucleophilic substitution.
R X + OH R OH + X
The nucleophilic substitution reactions are divided
into two types :
1. SN1 Reactions
2. SN2 Reactions
5. SN1 REACTIONS
SN1 stands for unimolecular nucleophilic substitution. When the rate
of a nucleophilic substitution reaction depends only on the
concentration of the alkyl halide, the reaction is of first order and is
represented as SN1.
The tertiary alkyl halides undergo hydrolysis by SN1 mechanism.
This is because the attack of the hydroxide ion on the crowded
tertiary alkyl halides is quite different.
6. KINETICS OF SN1 REACTION
The rate of SN1 reaction depends upon the concentration of alkyl
halide and is independent of the concentration of nucleophile. Thus
the reaction follows first order kinetics.
Rate α [alkyl halide]
Rate = k[(CH3)3C - Br
Reaction is called
unimolecular because the
rate determining step
involves only 1 molecule.
7. MECHANISM OF SN1 REACTION
SN1 reaction occurs in two steps.
Step 1: In first step, the carbon-halogen bond of tertiary butyl bromide
slowly breaks heterolytically to form an intermediate carbocation i.e. tert-
butyl carbocation.
Step 2: The carbocation formed combines rapidly with nucleophile i.e. OH
to give tertiary butyl alcohol.
Slow step is the rate determining step, thus step 1 is rate determining step.
8. This bond breaking is an example of heterolysis, cleavage in which
both bonding electrons go to the same fragment.
The combining of the carbocation with the hydroxide ion is a very
fast step, since it involves only the formation of a bond, an energy
releasing process.
This combining is recognized as an acid-base reaction in the Lewis
sense. Hydroxide ion is a strong base, carbocations are powerful
Lewis acids.
So here the rate-determining step involves only one molecule.
Any change in the rate of step 2 does not affect the overall rate.
9. STEREOCHEMISTRY OF SN1 REACTION
In SN1 reaction, carbocations are formed as an intermediate which
are triagonal and planar.
Carbocation has a flat structure so that nucleophile can attack it from
either side (i.e. front or back) resulting in the formation of two
products, one with retention of configuration and other with
inversion of configuration .
If the alkyl halide is optically active (i.e. when halogen carrying
carbon is chiral ), the product would be racemic mixture and
optically inactive.
In actual practice the, the product as a whole is not racemic. Usually
there is a larger proportion of molecules with inverted configuration
than of same configuration.
10. For eg, when (-)-2-bromoocatne is hydrolyzed by SN1 reaction,
partially racemized product is formed.
12. REACTIVITY OF ALKYL HALIDES TOWARDS SN1 REACTION
The rate of SN1 reaction depends on the stability of carbocation
formed. Therefore, the order of reactivity of alkyl halides towards
SN1 reaction is :
A tertiary carbocation is more stable than a secondary carbocation
which is more stable than a primary carbocation.
Greater the stability of carbocation, greater will be the ease of
formation of carbocation, and hence faster will be the rate of the
reaction.
13. EFFECT OF SOLVENT IN SN1 REACTION
A solvent that can facilitate the formation of the carbocation
intermediate will speed up the rate-determining step of SN1 reaction.
The preferred solvents are polar and protic.
The polar nature of solvents helps to stabilize ionic intermediates
whereas the protic nature of solvents helps to solvate the leaving
group.
Egs for solvents used in SN1 reactions include water and alcohol.
These solvents also act as nucleophiles.
14. REFERENCES
A textbook of organic chemistry, Arun Bahl, B S Bahl.
Sixth edition, Organic Chemistry, R T Morrison, R N Boyd.
www.organic-chemistry.org.
Organic Chemistry, Reaction and Reagents, O P Agarwal.