Graphite is an alltrop of carbon.
a.Define the term allotrop
b. Describe the structure and bonding in graphite and explain why graphite is used as pencil lead and conduct electricity
a. Allotropes are different forms of the same element that exist in various physical states and show different chemical and physical properties.
b. Graphite has a layered structure in which carbon atoms are arranged in hexagonal rings and covalently bonded to three other adjacent carbon atoms. The layers are held together by weak van der Waals forces. The layers can easily slide over each other, giving graphite its soft and slippery texture.
In a graphite pencil, when the pencil is rubbed against paper, small amounts of graphite are deposited onto the paper due to the weak interlayer forces, leaving an impression. This softness and the ability to leave marks on paper make graphite an ideal material for pencil leads.
Graphite is also a good conductor of electricity because of its unique structure. It has free electrons that are delocalized throughout the layers, allowing them to move and conduct electricity. Therefore, it is used in electrodes, batteries, and many other applications that require conductivity.
a.Cyclohexanol is oxidized to cyclohexanone using PCC. Show and explain this reaction mechanism
b. Write a detailed mechanism for the formation of an acetal from benzaldehyde and methanol in the presence of an acid catalyst
a. The oxidation of cyclohexanol to cyclohexanone using PCC (pyridinium chlorochromate) proceeds through a series of steps:
1. The PCC oxidant is converted to its active form, chromate(VI) ion, by reacting with a protonated pyridine species.
2. The chromate(VI) ion then attacks the hydroxyl group of cyclohexanol to form an ester intermediate.
3. The ester intermediate is then rapidly hydrolyzed to form the ketone product, cyclohexanone.
Overall, the reaction is a two-step process in which the hydroxyl group of cyclohexanol is oxidized to a ketone carbonyl group.
b. The formation of an acetal from benzaldehyde and methanol in the presence of an acid catalyst proceeds through the following steps:
1. The acid catalyst protonates the carbonyl group of benzaldehyde, making it more electrophilic.
2. Methanol then attacks the carbonyl group, forming a hemiacetal intermediate.
3. The acid catalyst then protonates the hydroxyl group of the hemiacetal, making it a better leaving group.
4. Methanol attacks the protonated hemiacetal, leading to the formation of the acetal product and regeneration of the acid catalyst.
Overall, the reaction is a four-step process in which the carbonyl group of benzaldehyde is attacked by methanol to form a hemiacetal intermediate, which then reacts further with methanol to form an acetal product.
Mechanism diagram of cyclohexanol is oxidized to cyclohexanone using PCC and explain this reaction mechanism
I'm sorry, as an AI language model, I don't have the ability to create images or diagrams. However, I can provide you with a detailed explanation of the mechanism of the oxidation of cyclohexanol to cyclohexanone using PCC.
The oxidation of cyclohexanol using PCC proceeds through an intermediate ester formation step. The reaction can be divided into two steps:
Step 1: Conversion of PCC to chromate(VI) ion
PCC is a complex of pyridine and chromic acid. It is first converted to its active form, chromate(VI) ion, by reacting with a protonated pyridine species.
Pyridine + HCrO3 -> PyH+ + CrO3-
Step 2: Oxidation of cyclohexanol to cyclohexanone
In the next step, the chromate(VI) ion attacks the hydroxyl group of cyclohexanol, forming an ester intermediate.
CrO3- + R-OH -> R-O-CrO3-
The ester intermediate then undergoes rapid hydrolysis to form the ketone product, cyclohexanone.
R-O-CrO3- + H2O -> R-CO + HCrO4-
Overall reaction:
C6H11OH + CrO3 + pyridine -> C6H10O + HCrO4- + pyridine-H+
Therefore, the complete oxidation of cyclohexanol to cyclohexanone using PCC proceeds through a two-step mechanism, in which chromate(VI) ion first attacks the hydroxyl group of cyclohexanol to form a chromate ester intermediate, which is then rapidly hydrolyzed to form the ketone product, cyclohexanone.
a. Allotropy refers to the existence of multiple forms of an element in the same physical state (solid, liquid, or gas) but with different structures and properties.
b. Graphite has a layered structure consisting of carbon atoms arranged in a honeycomb lattice. Each carbon atom is covalently bonded to three neighboring carbon atoms, forming strong sigma bonds within each layer. The layers are held together by weak van der Waals forces, allowing them to slide past each other easily.
The unique structure of graphite gives rise to its properties that make it suitable for pencil lead and electrical conductivity.
Pencil lead: The layers in graphite are held together by weak forces, allowing the layers to shed off onto paper or other surfaces, leaving a mark when used as pencil lead. The softness and low friction between the layers make it easy to write or draw with.
Electrical conductivity: In graphite, one carbon atom from each hexagon in the lattice donates its free electron to form a cloud of delocalized electrons above and below the layers. These delocalized electrons are free to move along the layers, making graphite an excellent conductor of electricity. The layers also provide a pathway for the electrons to flow through, resulting in its conductivity.
In summary, the unique structure and bonding in graphite, with its layered arrangement of carbon atoms, allow for easy sliding between layers (making it suitable for pencil lead) and provide a pathway for the flow of electrons (making it conductive).