FREE RADICAL REACTION OF ALKENE POSSESING TERTIARY HYDROGEN

 A free radical reaction involving an alkene typically refers to a reaction where a radical species (a molecule or atom with an unpaired electron) reacts with an alkene to form a new product. One common example of such a reaction is the addition of a halogen to an alkene, known as halogenation.

In halogenation, a halogen molecule (such as chlorine or bromine) breaks its covalent bond to form two halogen radicals. One of these halogen radicals then reacts with the alkene, forming a new carbon-halogen bond and generating an alkyl radical. The alkyl radical can then react with another halogen molecule to produce the final product.

When an alkene containing a tertiary hydrogen (a hydrogen atom bonded to a tertiary carbon atom) undergoes a free radical reaction, it can result in the formation of alkyl radicals and subsequent radical rearrangements. One common example is the reaction known as tertiary hydrogen abstraction.

In this reaction, a radical species abstracts a hydrogen atom from the tertiary carbon of the alkene, creating an alkyl radical and leaving behind a radical species on the alkene. The alkyl radical can then participate in various reactions depending on the reaction conditions and the nature of the radical species present.

ANSWER (d)

E2 REACTION (Part 1)

The E2 reaction involves the simultaneous removal of a leaving group and a hydrogen atom from adjacent carbon atoms to form a double bond. It occurs through a concerted mechanism, and its rate depends on the concentrations of the substrate and the base/nucleophile. Factors such as the strength of the base, stability of the leaving group, steric hindrance, and solvent effects influence the reaction.

When a bulky base reacts with a secondary alkyl halide, the reaction can proceed through E2 elimination. The bulky base abstracts a proton from the beta carbon adjacent to the halide, causing the leaving group to depart simultaneously. This results in the formation of a double bond. However, steric hindrance around the reacting carbon atoms may affect the rate and selectivity of the E2 reaction.

When a secondary alkyl halide reacts with a bulky base, the product outcome can vary in terms of regioselectivity, resulting in either the Zaitsev or Hofmann product. Zaitsev product is typically favored in most E2 reactions, there are cases where the Hofmann product can be the major or exclusive product, especially when steric hindrance is significant. The actual product distribution will depend on the specific reaction conditions and the substrate used.

When 2-bromobutane reacts with tert-butoxide (t-BuO-), a strong and bulky base, an E2 elimination reaction can occur.

In this reaction, the tert-butoxide acts as a base and abstracts a proton from the beta carbon (adjacent to the bromine) in 2-bromobutane. At the same time, the bromine atom serves as the leaving group. This leads to the formation of a double bond, resulting in the production of 2-butene. Additionally, tert-butyl bromide is generated as a byproduct.

The use of tert-butoxide as a bulky base can influence the regioselectivity of the reaction. The steric hindrance provided by the bulky tert-butoxide can hinder the approach to the more substituted beta carbon. As a result, the reaction may exhibit some degree of Hofmann product selectivity, leading to the formation of the less substituted alkene in some cases.

ANSWER (b)

E1 REACTION (Part 1)

 E1 reaction, also known as Elimination-Unimolecular reaction, is a type of chemical reaction that involves the removal of a leaving group and a proton from adjacent carbon atoms in a molecule, resulting in the formation of a double bond.

The reaction mechanism involves a two-step process: in the first step, a leaving group departs from the molecule, generating a carbocation intermediate. In the second step, a proton is removed from an adjacent carbon atom, resulting in the formation of a double bond and the regeneration of a protonated leaving group.

E1 reactions typically occur in the presence of a strong base or heat, and they are most commonly observed in reactions involving secondary or tertiary alkyl halides. The rate of an E1 reaction depends only on the concentration of the substrate, as the reaction involves the formation of a carbocation intermediate that can be stabilized by neighboring groups.

Zaitsev and Hoffman products refer to two possible products that can be formed during an elimination reaction, particularly when a base is used to remove a proton from a beta-carbon atom in a molecule.

The Zaitsev product is the more stable and predominant product, which is formed when the elimination reaction occurs through the transition state that leads to the most substituted alkene. This product is also known as the "Saytzeff" product.

On the other hand, the Hoffman product is the less stable and less substituted product, which is formed when the elimination reaction occurs through the transition state that leads to the least substituted alkene. This product is also known as the "anti-Zaitsev" product.

The preference for the formation of Zaitsev or Hoffman products depends on the reaction conditions, the nature of the substrate, and the strength of the base used. Generally, Zaitsev products are favored in reactions involving strong bases and substrates that can stabilize the negative charge of the alkene intermediate through resonance or inductive effects. Meanwhile, Hoffman products are favored in reactions involving weaker bases or substrates that cannot stabilize the negative charge of the alkene intermediate.

It is important to note that while Zaitsev products are generally more stable and predominant, there are some instances where Hoffman products may be preferred, such as when steric hindrance around the beta-carbon atom makes it difficult for the base to approach and remove the proton from that position.

ANSWER (a)

Dehydration of Tertiary Alcohol

The dehydration of tertiary alcohols follows the E1 mechanism (elimination unimolecular), which involves the formation of a carbocation intermediate.

In the first step of the reaction, a proton from the beta-carbon adjacent to the hydroxyl group is removed by a strong acid, such as sulfuric acid (H₂SO₄) or phosphoric acid (H₃PO₄), resulting in the formation of a carbocation intermediate. Tertiary carbocations are relatively stable due to the presence of three alkyl groups that can stabilize the positive charge of the carbocation.

In the second step, a water molecule acts as a base and removes a proton from the beta-carbon, leading to the formation of a double bond and the release of a protonated water molecule (H3O+). The resulting product is an alkene, which is typically the major product of the reaction.

The (c) is the major product, (b) and (d) are the minor product. The (a) is not the product because the proton that has been remove is not in beta position. Furthermore, the hydride shift do not occur because its already tertiary carbocation.

JABIR IBN HAYYAN: Bapa Kimia Dunia Islam

 

Jabir ibn Hayyan, juga dikenali sebagai Geber di dunia Barat, adalah seorang ahli alkimia, ahli kimia, dan ahli falsafah terkemuka yang hidup pada abad ke-8 di Iran kini. Beliau dianggap sebagai salah satu tokoh paling penting dalam sejarah kimia dan alkimia, dan karyanya mempunyai impak yang signifikan terhadap perkembangan kedua-dua bidang tersebut.

Jabir ibn Hayyan dilahirkan di bandar Tus di Iran, sekitar tahun 721 Masihi. Beliau menerima pendidikan di Kufa, yang merupakan pusat pembelajaran pada masa itu, dan kemudian berpindah ke Baghdad, di mana beliau meneruskan kajian dan eksperimennya. Jabir ibn Hayyan dikenal pasti dengan pendekatan eksperimentalnya dalam alkimia, yang melibatkan pengujian teorinya melalui eksperimen praktikal dan pemerhatian.

Jabir ibn Hayyan menulis lebih daripada 3,000 karya dalam pelbagai subjek, termasuk kimia, alkimia, falsafah, perubatan, dan astrologi. Beliau dikenal pasti dengan sumbangan terhadap perkembangan pelbagai proses kimia, seperti penyulingan alkohol dan penyediaan asid. Beliau juga berminat dalam transmutasi logam, dan beliau percaya bahawa ia mungkin untuk menukar logam asas menjadi emas.

Karya Jabir ibn Hayyan diterjemahkan ke bahasa Latin semasa zaman Pertengahan, dan idea-ideanya mempunyai impak yang signifikan terhadap perkembangan alkimia dan kimia Barat. Pendekatan beliau terhadap eksperimen dan penekanan pada pemerhatian dan pengalaman praktikal adalah instrumental dalam membentuk kaedah sains, yang masih digunakan hari ini.

Secara keseluruhannya, sumbangan Jabir ibn Hayyan terhadap bidang kimia dan alkimia, serta pengaruhnya terhadap perkembangan sains dan falsafah, menjadikannya salah satu tokoh yang paling penting dalam sejarah sains.

 

 

 

 

SN2 REACTION (Part 1)

The SN2 (substitution nucleophilic bimolecular) reaction is a type of chemical reaction that involves the replacement of a leaving group (such as a halogen) in a molecule with a nucleophile (an atom or group of atoms with a pair of electrons to donate). The reaction occurs in one step, where the nucleophile attacks the carbon atom attached to the leaving group, and the leaving group departs at the same time. The reaction is called SN2 because it involves two molecules interacting with each other, namely the nucleophile and the molecule with the leaving group.

SN2 reactions are typically observed in alkyl halides, where the carbon atom attached to the halogen is also bonded to one or two other carbon atoms. The reaction proceeds through a transition state in which the nucleophile forms a new bond with the carbon atom, while the leaving group departs with a pair of electrons. SN2 reactions are known to invert the stereochemistry of the molecule, meaning that the arrangement of atoms around the carbon center is reversed from its starting configuration. SN2 reactions are important in many fields, including organic chemistry, biochemistry, and pharmaceuticals.

ANSWER (C)

EXPLAINATION

The rate of an SN2 reaction depends on several factors, including the steric hindrance around the carbon center, the strength of the bond between the leaving group and the carbon atom, and the basicity and nucleophilicity of the attacking nucleophile. Based on these factors, the reactivity of the given compounds towards SN2 reaction can be ranked as follows:

1-chloro-1-cyclohexyl methane (I) - This compound has the most steric hindrance around the carbon center due to the presence of two bulky cyclohexyl groups. This steric hindrance makes it difficult for the attacking nucleophile to access the carbon center, and as a result, the reaction rate is expected to be the slowest among the given compounds.

1-chlorocyclohexane (II) - This compound has a bulky cyclohexyl group, which makes the carbon center more hindered, thereby slowing down the rate of SN2 reaction. However, the reaction can still occur due to the moderately good leaving group (chloride ion).

1-iodobutane (III) - This compound is expected to undergo SN2 reaction the fastest because iodine is a good leaving group, and the carbon center is relatively unhindered. Additionally, the high polarizability of the iodine atom makes it easier for the nucleophile to attack the carbon center.

1-chlorobutane (IV) - This compound is also expected to undergo SN2 reaction relatively quickly due to the relatively low steric hindrance around the carbon center, and the chloride ion is a moderately good leaving group.

Overall, 1-iodobutane is expected to undergo SN2 reaction the fastest, while 1-chloro-1-cyclohexyl methane is expected to be the slowest

FUEL CELL

 

Fuel Cell merupakan peranti elektrokimia yang menukar tenaga kimia bahan bakar dan agen pengoksidasi menjadi tenaga elektrik melalui tindak balas kimia. Ia merupakan sumber tenaga yang amat berkesan dan bersih yang semakin menarik perhatian dalam beberapa tahun terakhir kerana potensinya untuk mengurangkan pelepasan gas rumah hijau dan meningkatkan kecekapan tenaga.

Fuel Cell  berfungsi dengan menggabungkan bahan bakar seperti hidrogen atau metana, dan agen pengoksidasi seperti oksigen atau udara, untuk menghasilkan elektrik, air, dan haba. Bahan bakar dan agen pengoksidasi disalurkan ke sel bahan bakar melalui saluran berasingan, dan mereka bertindak balas di atas permukaan elektrod, biasanya terbuat daripada platinum, yang disaluti dengan bahan khas yang dipanggil elektrolit. Elektrolit memudahkan pemindahan elektron antara bahan bakar dan agen pengoksidasi, membolehkan sel bahan bakar menghasilkan elektrik.

Salah satu kelebihan utama Fuel Cell adalah kecekapan tinggi mereka. Berbeza dengan enjin pembakaran tradisional, yang hanya menukar sebahagian kecil tenaga dalam bahan bakar menjadi kerja yang berguna, sel bahan bakar boleh menukar sehingga 60% tenaga dalam bahan bakar menjadi elektrik, menjadikannya sebagai sumber tenaga yang amat berkesan dan menjimatkan kos. Selain itu, Fuel Cell bersih dan tidak menghasilkan sebarang pelepasan yang berbahaya, menjadikannya sebagai pilihan yang menarik untuk mengurangkan pelepasan gas rumah hijau dan pencemaran udara.

Fuel Cell boleh digunakan dalam pelbagai aplikasi, dari peranti mudah alih kecil seperti laptop dan telefon bimbit, hingga sistem tetap yang lebih besar seperti bekalan tenaga cadangan untuk bangunan dan sistem tenaga jauh untuk aplikasi luar rangkaian. Ia juga boleh digunakan dalam pengangkutan, dengan kenderaan Hydrogen Fuel Cell menawarkan alternatif yang menjanjikan kepada kenderaan petrol dan diesel tradisional.

Walaupun terdapat banyak kelebihan, Fuel Cell masih menghadapi beberapa cabaran yang perlu ditangani sebelum mereka boleh menjadi sumber tenaga yang meluas dan komersial. Salah satu cabaran utama adalah kos pengeluaran dan penggunaan sistem Fuel Cell yang masih agak tinggi berbanding dengan sumber tenaga tradisional. Selain itu, infrastruktur untuk pengeluaran, pengangkutan, dan penyimpanan hidrogen, bahan bakar yang paling biasa untuk Fuell Cell, masih belum cukup memadai dan perlu diperluaskan.

Kesimpulannya, Fuel Cell adalah sumber tenaga yang amat menjanjikan dan efisien yang mempunyai potensi untuk mengubah cara kita menghasilkan dan menggunakan tenaga. Walaupun terdapat cabaran yang perlu ditangani, minat dan pelaburan yang meningkat dalam

AN ALKANE

Alkanes are a type of organic compound that is composed solely of carbon and hydrogen atoms, with only single bonds between them. They are also known as paraffins or saturated hydrocarbons, due to their highly stable and non-reactive nature.

The simplest form of an alkane is methane, which has one carbon atom and four hydrogen atoms, and is commonly found in natural gas. The larger alkanes, such as ethane, propane, butane, and pentane, are commonly used as fuels in the form of liquefied petroleum gas (LPG) or as components of gasoline.

One of the unique properties of alkanes is that they are highly resistant to chemical reactions, due to the strength and stability of the carbon-carbon and carbon-hydrogen bonds. This makes them ideal for use as fuels, as they can burn cleanly and efficiently, with minimal byproducts or pollutants.

Alkanes can also be used in a variety of industrial applications, such as in the production of plastics, solvents, and synthetic materials. For example, the polymerization of ethene, which is derived from the cracking of crude oil, can result in the production of polyethylene, a commonly used plastic material.

Despite their non-reactive nature, alkanes can still undergo certain chemical reactions, such as combustion, halogenation, and oxidation. These reactions can be useful in various applications, such as in the production of organic compounds and in the removal of pollutants from the environment.

One of the challenges with using alkanes as a fuel source is their limited supply, as they are derived primarily from fossil fuels, such as petroleum and natural gas, which are finite resources. This has led to increasing efforts to develop alternative, renewable sources of fuel, such as biofuels and hydrogen.

In conclusion, alkanes are a highly stable and versatile class of organic compounds that have a wide range of industrial and commercial applications. While their non-reactive nature makes them ideal for use as fuels, their limited supply highlights the need for continued research and development into alternative, sustainable sources of energy.

ILMU PENEGETAHUAN

Ilum engetahuan sering dianggap sebagai salah satu aset paling berharga yang dimiliki oleh individu atau organisasi. Ia adalah pemahaman dan kesedaran tentang maklumat dan pengalaman yang membolehkan kita menavigasi dunia dan membuat keputusan yang berasaskan fakta.

Dalam dunia yang semakin cepat berubah dan kompleks hari ini, pengetahuan menjadi semakin penting. Di setiap bidang dan industri, pembangunan dan kemajuan baru terus berlaku, dan mereka yang mempunyai pengetahuan yang terkini dan relevan adalah mereka yang paling berpotensi untuk berjaya.

Salah satu manfaat penting pengetahuan adalah memberi kekuatan kepada kita untuk membuat keputusan yang lebih baik. Apabila kita mempunyai pemahaman yang mendalam tentang suatu subjek, kita lebih bersedia untuk menimbang segala pro dan kontra pilihan yang ada dan memilih tindakan terbaik. Ini adalah benar sama ada kita membuat keputusan peribadi tentang kesihatan atau kewangan kita, atau keputusan strategik tentang kerjaya atau perniagaan kita.

Selain membantu kita membuat keputusan yang lebih baik, pengetahuan juga membolehkan kita untuk berinovasi dan mencipta. Sama ada kita sedang mengembangkan teknologi baru, mengehasilkan produk baru, atau merancang strategi perniagaan baru, kemampuan kita untuk mencari penyelesaian kreatif adalah terus berkaitan dengan pemahaman kita tentang bidang yang kita kerjakan.

Selain itu, pengetahuan juga berpotensi untuk mengubah hidup kita dalam berbagai cara. Ia dapat memberikan kita rasa tujuan dan kepuasan yang lebih besar, memperluas wawasan kita, dan membantu kita berhubung dengan orang lain yang mempunyai minat dan hasrat yang sama.

Walau bagaimanapun, memperoleh dan menjaga pengetahuan tidak selalu mudah. Ia memerlukan pelaburan yang signifikan dalam masa, usaha, dan sumber daya. Ia juga memerlukan keberanian untuk mencabar asumsi dan kepercayaan kita, dan untuk terbuka terhadap ide dan pandangan baru.

Walau bagaimanapun, kepentingan pengetahuan tidak dapat diabaikan. Sama ada kita mencari pertumbuhan peribadi, kejayaan profesional, atau impak sosial, pengetahuan adalah kunci yang membuka potensi kita dan membolehkan kita mencapai matlamat kita. Oleh itu, jangan pernah berhenti belajar, meneroka, dan memperluas pemahaman kita tentang dunia di sekeliling kita.

HOMOLOG SERIES

Homolog series, also known as homologous series, are groups of organic compounds that have a similar structure and chemical properties, with their successive members differing by a constant increment of a repeating unit, such as a CH2 group. Homologous series play an important role in organic chemistry because they allow chemists to predict the physical and chemical properties of new compounds based on the properties of known compounds in the same series. In this blog post, we will explore the concept of homolog series in more detail.

Structure of Homolog Series

Homolog series are composed of compounds that have a similar structure and chemical properties. The successive members of the series differ by a constant increment of a repeating unit, such as a CH2 group. For example, the alkanes (a type of hydrocarbon) form a homologous series in which the successive members differ by a CH2 group. The first member of the series is methane (CH4), followed by ethane (C2H6), propane (C3H8), butane (C4H10), pentane (C5H12), and so on.

Physical Properties of Homolog Series

The physical properties of homologous series follow a predictable pattern. For example, as the number of carbon atoms in the chain increases in the alkanes, the boiling point and melting point of the compound also increase. This is because longer hydrocarbon chains have a greater surface area and stronger intermolecular forces, which require more energy to overcome.

Chemical Properties of Homolog Series

The chemical properties of homologous series also follow a predictable pattern. For example, the alkanes are relatively unreactive because they have a strong C-C and C-H bond. However, as the number of carbon atoms in the chain increases, the reactivity of the compound also increases. This is because longer hydrocarbon chains have a greater surface area and are more likely to undergo reactions such as combustion, oxidation, and substitution.

Applications of Homolog Series

Homolog series have many practical applications in organic chemistry. For example, chemists can use the properties of known compounds in a homologous series to predict the properties of new compounds in the same series. This can be useful in drug discovery, where chemists can design new drugs based on the properties of existing drugs in the same homologous series. Homolog series can also be used in the petroleum industry to predict the properties of different types of crude oil, which can then be used to refine different types of fuels.

Conclusion

Homolog series are groups of organic compounds that have a similar structure and chemical properties, with their successive members differing by a constant increment of a repeating unit, such as a CH2 group. The physical and chemical properties of homologous series follow a predictable pattern, which makes them useful in predicting the properties of new compounds in the same series. Homolog series have many practical applications in organic chemistry, including drug discovery and the petroleum indust