Chapter 12 Introduction to Organic Chemistry: Alkanes

Naming of Disubstituted Cycloalkanes

2. Number the ring in the direction that will give both substituents the lowest numbers possible. Also, ethyl must have the smallest number as it takes priority alphabetically Option 1: Yes Option 2: No! So, the name is 1-Ethyl-3-methylcyclohexan

Naming Alkanes

Straight Chain Alkanes: Suffix, the end of the name, is always ane. Prefix, the beginning of the name , is in accordance with the number of carbons

Functional Groups

• Defined as: an atom or group of atoms within a molecule that has a characteristic physical and chemical behavior. • Each functional group is part of a larger molecule • Molecules may have more than one class of functional group present. • A given functional group tends to undergo the same reactions in every molecule that contains it, regardless of the size or complexity of that molecule

Alternative Ways of Representing Organic Structures

Lewis==> Condensed structure==>skeletal structure/Line structure

Reactions of Alkanes

1. Combustion • Reaction with O2 to produce CO2 and water; large amount of energy released • Example: • CH4(g) + O2(g)→CO2(g) + H2O(g)

Naming of Disubstituted Cycloalkanes

1. Identify the ring (shown in red) and the substituents (shown in green) There are 6 carbons in the ring so the end of the name is cyclohexane There are 2 methyls off the ring so we need the prefix di

Naming of Disubstituted Cycloalkanes

1. Identify the ring (shown in red) and the substituents (shown in green) There are 6 carbons in the ring so the end of the name is cyclohexane There is an ethyl and a methyl group

Naming Alkanes

1. Locate the parent chain (longest chain in the molecule); it can turn corners! 2. Locate the branches and number the parent chain so that the branches have the smallest numbers 3. Identify the type of branch: 4. Place branches in alphabetical order 5. If you have more than one of the same kind of branch, use di, tri, tetra. Note these don't affect the alphabetization

Naming of Disubstituted Cycloalkanes

2. Number the ring in the direction that will give both substituents the lowest numbers possible so: Option 1: Yes Option 2: No! So, the name is 1,2-Dimethylcyclohexane

• What are addition reactions?

Addition reactions are a type of chemical reaction in which atoms or groups of atoms are added to a molecule, resulting in the formation of a new compound. In an addition reaction, two or more reactants combine to form a single product, with no by-products produced. Addition reactions can involve a variety of different types of compounds, including alkenes, alkynes, aldehydes, ketones, and others. For example, in the addition of hydrogen gas to an alkene, the double bond is broken and the two hydrogen atoms are added to the two carbon atoms that were originally part of the double bond. Addition reactions are often used in organic chemistry to create new compounds with specific properties or to modify existing compounds. They are also important in the production of many industrial and consumer products, including plastics, pharmaceuticals, and fuels.

• How can we describe addition reactions reactions?

Addition reactions can be described in several ways, depending on the specific reaction and the level of detail required. Here are a few ways to describe addition reactions: Chemical equation: Addition reactions can be represented using a chemical equation, which shows the reactants on the left side and the products on the right side. For example, the addition of hydrogen gas to an alkene can be represented by the equation: Alkene + H2 → Alkane Structural formula: Addition reactions can also be represented using structural formulas, which show the arrangement of atoms in the reactants and products. For example, the addition of hydrogen gas to ethene can be represented by the structural formula: H2C=CH2 + H2 → H3C-CH3 Mechanism: A mechanism is a detailed description of the step-by-step process by which a reaction occurs. Addition reactions often involve several intermediate steps, and understanding the mechanism can provide insight into the factors that influence the reaction. For example, the addition of HBr to an alkene can occur through a mechanism that involves the formation of a carbocation intermediate. Stereochemistry: Addition reactions can also be described in terms of their stereochemistry, which refers to the three-dimensional arrangement of atoms in the product. For example, the addition of hydrogen to an alkene can result in the formation of a chiral center if the original alkene was a stereoisomer. Overall, describing addition reactions involves understanding the reactants, products, mechanism, and stereochemistry of the reaction.

• How do we name alkanes?

Alkanes are a family of organic compounds that contain only carbon-carbon single bonds and are therefore saturated with hydrogen. Here's how to name alkanes: Count the number of carbon atoms in the longest continuous chain of carbons (the parent chain). Use the appropriate prefix to indicate the number of carbon atoms in the parent chain: Meth- for one carbon Eth- for two carbons Prop- for three carbons But- for four carbons Pent- for five carbons Hex- for six carbons Hept- for seven carbons Oct- for eight carbons Non- for nine carbons Dec- for ten carbons Add the suffix "-ane" to indicate that the compound is an alkane. Number the carbon atoms in the parent chain so that the substituents (if any) have the lowest possible numbers. The numbering should begin at the end of the chain closest to the first substituent, even if there are other substituents closer to the other end of the chain. Use the appropriate prefix to indicate the number of substituents of each type. Some common prefixes include: Methyl- for a -CH3 group Ethyl- for a -CH2CH3 group Propyl- for a -CH2CH2CH3 group Butyl- for a -CH2CH2CH2CH3 group Name the substituents in alphabetical order, ignoring any prefixes such as "iso" or "neo". If two or more substituents are identical, use prefixes such as "di-" or "tri-" to indicate the number of times the substituent appears. Combine the names of the parent chain and the substituents, listing the substituents in alphabetical order and using hyphens to separate the numbers and names. Here's an example: CH3-CH2-CH(CH3)-CH2-CH3 The parent chain has five carbon atoms, so it is a pentane. There is one methyl (-CH3) substituent on the third carbon atom of the chain. The name of the compound is 3-methylpentane. Note that the numbering of the carbon atoms is critical in determining the correct name of the compound.

• What reactions do alkanes undergo?

Alkanes are relatively unreactive compounds due to the strength of the carbon-carbon and carbon-hydrogen single bonds in their structures. However, alkanes can undergo certain reactions under specific conditions. Here are some examples of reactions that alkanes can undergo: Combustion: Alkanes can undergo combustion reactions in the presence of oxygen to produce carbon dioxide and water. This reaction is highly exothermic and releases a large amount of heat energy. The general combustion reaction for an alkane can be represented by the equation: alkane + oxygen → carbon dioxide + water Halogenation: Alkanes can undergo halogenation reactions in the presence of a halogen, such as chlorine or bromine, to form alkyl halides. The reaction proceeds via a free radical mechanism and can result in multiple products due to the multiple possible substitution sites in the alkane molecule. Cracking: Alkanes can undergo cracking reactions under high temperature and pressure to break down into smaller hydrocarbons. This process is important in the petroleum industry for producing fuels and other chemicals from crude oil. Isomerization: Alkanes can undergo isomerization reactions, where they are converted into different structural isomers. This reaction is often catalyzed by an acid or a metal catalyst. Dehydrogenation: Alkanes can undergo dehydrogenation reactions, where they lose hydrogen atoms to form alkenes. This reaction is also often catalyzed by a metal catalyst. It's important to note that the reactivity of alkanes is limited due to their high stability and lack of functional groups that can undergo substitution or addition reactions.

Properties of Alkanes

Alkanes contain only nonpolar C-C and C-H bonds. Overall nonpolar molecules; London dispersion/Van de Waals forces. • The effect of these forces is shown in the regularity with which the melting and boiling points of straight-chain alkanes increase with molecular size. - The first four alkanes, methane, ethane, propane, and butane, are gases at room temperature and pressure. - Alkanes with 5-15 carbon atoms are liquids. - Alkanes with 16 or more carbon atoms are generally low-melting, waxy solids.

Halogenation: Comparison to Alkanes

Alkenes more reactive than alkanes. Goal is to get to saturation!

Alternative Ways of Representing Organic Structures

Condensed structure: C-C and C-H bonds are not shown. The only line/bond present is from the straight chain to the "branch". Skeletal/Line structure: 1. Anywhere a line ends or begins represents a C atom. Also the intersection of two lines is a C atom. 2. Each carbon-carbon bond is represented by a line. 3. Any type of atom, other than C or H, must be shown. 4. All bonds not shown for any C are carbon-hydrogen bonds; the number of which is equal to the number needed to ensure that C has 4 bonds

• What are conformers and isomers and how do we draw them?

Conformers and isomers are two types of molecules that differ in their spatial arrangement of atoms. Here's how to define and draw each type: Conformers: Conformers are different conformations (shapes) of the same molecule that can interconvert by rotation around single bonds. In other words, conformers are different ways that a molecule can twist or bend without breaking any bonds. Conformers can be classified as either "staggered" or "eclipsed" based on the angle between the atoms in the molecule. To draw a conformer, follow these steps: Draw the basic structure of the molecule. Identify the rotatable bonds in the molecule. Draw the molecule in the desired conformer by rotating the atoms around the rotatable bond. The most stable conformer is usually the staggered conformer, where the atoms are farthest apart from each other. Isomers: Isomers are different molecules that have the same molecular formula but different arrangements of atoms. There are two types of isomers: structural isomers and stereoisomers. Structural isomers have different bonding patterns between atoms. For example, butane and methylpropane are structural isomers because they have different arrangements of carbon and hydrogen atoms. Stereoisomers have the same bonding pattern but differ in their three-dimensional arrangement of atoms. There are two types of stereoisomers: enantiomers and diastereomers. To draw isomers, follow these steps: Identify the molecular formula of the molecule. Draw the basic structure of the molecule in different arrangements of atoms. Check if the different structures have the same molecular formula. If they do, then they are isomers of each other. Note that the most stable conformer and the most prevalent isomer of a molecule depend on various factors such as steric hindrance, bond angles, and electronic repulsion.

• What are the structures and properties of the cycloalkanes?

Cycloalkanes are a type of organic compound that contain one or more rings of carbon atoms. The simplest cycloalkane is cyclopropane, which has a three-membered ring, and the most commonly studied cycloalkane is cyclohexane, which has a six-membered ring. Here are some general structures and properties of cycloalkanes: Structure: Cycloalkanes are ring structures that have the same general formula as their linear alkane counterparts (CnH2n), but have two fewer hydrogen atoms. The carbon atoms in cycloalkanes are sp3 hybridized and are arranged in a ring, with each carbon bonded to two other carbons and two hydrogen atoms. Conformation: Cycloalkanes can exist in different conformations due to the freedom of rotation around their carbon-carbon bonds. The most stable conformation of cycloalkanes is the chair conformation, which has no angle strain and no torsional strain. Other conformations, such as boat and twist-boat, have higher energy due to angle strain and/or torsional strain. Physical properties: The physical properties of cycloalkanes depend on their molecular size and shape. Generally, cycloalkanes are nonpolar compounds with low solubility in water and high solubility in nonpolar solvents such as hexane and cyclohexane. Cycloalkanes have higher boiling points and melting points than their linear alkane counterparts due to the ring strain and stronger intermolecular forces between molecules. Reactivity: Cycloalkanes are relatively unreactive compounds due to their high stability and lack of functional groups. However, they can undergo reactions such as hydrogenation, halogenation, and nitration under specific conditions. The reactivity of cycloalkanes is influenced by the ring strain and the presence of substituents on the ring. In summary, cycloalkanes are a type of organic compound that contain one or more rings of carbon atoms. They have unique structures and properties that are different from their linear alkane counterparts, and they can undergo certain reactions under specific conditions.

• What are functional groups and how do we identify them in compounds?

Functional groups are specific groups of atoms or bonds within a molecule that are responsible for the characteristic chemical properties of that molecule. They are defined as a group of atoms or bonds that behave in a predictable way and exhibit similar chemical and physical properties regardless of the rest of the molecule. Functional groups can be identified in compounds by their characteristic chemical and physical properties, as well as by their infrared (IR) spectra, mass spectra, and nuclear magnetic resonance (NMR) spectra. Common functional groups in organic chemistry include: Hydroxyl (-OH): This group consists of an oxygen atom bonded to a hydrogen atom and is found in alcohols, phenols, and carboxylic acids. It can be identified by a broad, intense absorption peak in the IR spectrum around 3300 cm-1. Carbonyl (>C=O): This group consists of a carbon atom double-bonded to an oxygen atom and is found in aldehydes, ketones, and carboxylic acids. It can be identified by a sharp absorption peak in the IR spectrum around 1700 cm-1. Amine (-NH2): This group consists of a nitrogen atom bonded to two hydrogen atoms and is found in amines and amino acids. It can be identified by a characteristic N-H stretching vibration in the IR spectrum around 3300 cm-1. Ester (-COO-): This group consists of a carbonyl group bonded to an oxygen atom, which is in turn bonded to a carbon atom. It is found in esters and carboxylic acids. It can be identified by a sharp absorption peak in the IR spectrum around 1735 cm-1. Alkene (-C=C-): This group consists of a carbon-carbon double bond and is found in alkenes and other unsaturated hydrocarbons. It can be identified by a characteristic stretching vibration in the IR spectrum around 1650 cm-1. There are many other functional groups in organic chemistry, and their identification requires a combination of chemical and spectroscopic techniques.

Functional Groups

Here is a list of some common functional groups in organic chemistry: Alkyl (-R): a group consisting of a chain of carbon and hydrogen atoms. Alkene (>C=C<): a group consisting of a carbon-carbon double bond. Alkyne (>C≡C<): a group consisting of a carbon-carbon triple bond. Alcohol (-OH): a group consisting of a hydroxyl (-OH) group bonded to a carbon atom. Amine (-NH2): a group consisting of a nitrogen atom bonded to one, two, or three carbon atoms. Carbonyl (>C=O): a group consisting of a carbon atom double-bonded to an oxygen atom. Carboxylic Acid (-COOH): a group consisting of a carbonyl group (-C=O) and a hydroxyl group (-OH) bonded to the same carbon atom. Ester (-COO-): a group consisting of a carbonyl group (-C=O) and an ether (-O-) group bonded to the same carbon atom. Ether (-O-): a group consisting of an oxygen atom bonded to two carbon atoms. Halide (-X): a group consisting of a halogen atom (such as fluorine, chlorine, bromine, or iodine) bonded to a carbon atom. Nitrile (-C≡N): a group consisting of a carbon atom triple-bonded to a nitrogen atom. Phenyl (C6H5-): a group consisting of a six-carbon aromatic ring. Sulfide (-S-): a group consisting of a sulfur atom bonded to two carbon atoms. Thiol (-SH): a group consisting of a sulfur atom bonded to a hydrogen atom. These functional groups are important in determining the properties and reactivity of organic compounds.

Naming of Monosubstituted Cycloalkanes

Identify the ring (shown in red) and the substituent (shown in green) There are 6 carbons in the ring so the end of the name is cyclohexane There is an ethyl group off the ring The name is: Ethylcyclohexane Numbering system is not employed with just one substituent!

• How do we identify types of carbons?

In organic chemistry, there are several types of carbon atoms that can be distinguished based on their chemical and physical properties. Here are some common types of carbons and how to identify them: Primary carbon: A primary carbon is a carbon atom that is bonded to one other carbon atom. Secondary carbon: A secondary carbon is a carbon atom that is bonded to two other carbon atoms. Tertiary carbon: A tertiary carbon is a carbon atom that is bonded to three other carbon atoms. Quaternary carbon: A quaternary carbon is a carbon atom that is bonded to four other carbon atoms. To identify the types of carbons in a molecule, you can follow these steps: Identify the carbon atoms in the molecule. Count the number of other carbon atoms that are directly bonded to each carbon atom. Classify each carbon atom as primary, secondary, tertiary, or quaternary based on the number of other carbon atoms it is bonded to. For example, consider the molecule 2,3-dimethylbutane: CH3-CH(CH3)-CH(CH3)-CH3 The carbon atom at the end of the chain is a primary carbon because it is bonded to only one other carbon atom. The two carbon atoms in the middle of the chain are secondary carbons because they are each bonded to two other carbon atoms. The carbon atom in the center of the molecule is a tertiary carbon because it is bonded to three other carbon atoms. Identifying the types of carbons in a molecule can be useful in predicting the reactivity and behavior of the molecule in various chemical reactions.

What does organic chemistry entail?

Organic chemistry is the study of the structure, properties, reactions, and synthesis of organic compounds, which are compounds that contain carbon atoms. Organic chemistry is a vast and complex field that encompasses a wide range of topics, including the study of biomolecules such as DNA, proteins, and carbohydrates, as well as the synthesis of drugs, polymers, and materials. In organic chemistry, researchers investigate the properties of organic compounds, such as their chemical and physical properties, as well as how they react with other substances. They also study the mechanisms of chemical reactions, the use of various laboratory techniques and instrumentation, and the development of new methods for synthesizing organic compounds. Some of the major areas of study in organic chemistry include: Structure and bonding: understanding the structure of organic compounds and the types of bonds between atoms. Reactivity: studying the ways in which organic compounds can react with other substances, including acids, bases, and oxidizing agents. Synthesis: developing new methods for synthesizing organic compounds, including the use of catalysts, reagents, and other chemical reactions. Spectroscopy: using various spectroscopic techniques to analyze the chemical and physical properties of organic compounds. Overall, organic chemistry plays a critical role in many areas of science and industry, including medicine, materials science, agriculture, and environmental science.

Characteristics of Organic Compounds

Organic compounds are a large class of chemical compounds that are characterized by the presence of carbon atoms covalently bonded to other elements, most commonly hydrogen, oxygen, nitrogen, sulfur, and halogens. Some of the characteristics of organic compounds include: Covalent bonding: Organic compounds are typically held together by covalent bonds, which are formed by the sharing of electrons between atoms. Low melting and boiling points: Most organic compounds have relatively low melting and boiling points compared to inorganic compounds due to their weak intermolecular forces. Solubility in organic solvents: Many organic compounds are soluble in nonpolar organic solvents such as ether, benzene, and chloroform, but insoluble in polar solvents such as water. Isomerism: Organic compounds often exhibit isomerism, which is the existence of compounds with the same molecular formula but different structural arrangements of their atoms. Functional groups: Organic compounds contain characteristic functional groups that determine their chemical and physical properties. Combustibility: Organic compounds are typically flammable and undergo combustion to produce carbon dioxide and water. Biological activity: Many organic compounds are biologically active and are essential for life processes, such as amino acids, nucleic acids, carbohydrates, and lipids. Overall, organic compounds exhibit a wide range of physical and chemical properties and play an important role in many aspects of everyday life, including food, pharmaceuticals, fuels, and materials science.

• How do we define organic compounds?

Organic compounds are compounds that contain carbon and are found in living organisms. The study of organic chemistry focuses on the properties, structure, and reactions of these carbon-containing compounds. However, not all compounds that contain carbon are considered organic. For example, carbonates, carbides, and cyanides are compounds that contain carbon but are not classified as organic compounds. In general, organic compounds are characterized by their ability to form covalent bonds with other elements, including carbon, hydrogen, oxygen, nitrogen, sulfur, and halogens. They can exist as simple molecules, such as methane (CH4), or complex macromolecules, such as proteins and DNA. Organic compounds play a crucial role in many biological processes, including metabolism, growth, and reproduction. They are also widely used in industry for the production of plastics, fuels, drugs, and many other products.

• What are straight chain and branched chain alkanes?

Straight-chain and branched chain alkanes are both types of hydrocarbons, which are organic compounds that consist entirely of hydrogen and carbon atoms. Alkanes are a class of hydrocarbons that have only single bonds between carbon atoms and are often referred to as "saturated" hydrocarbons. Straight chain alkanes, also known as normal alkanes, are alkanes that have a continuous, unbranched chain of carbon atoms. They have the general formula CnH2n+2, where n represents the number of carbon atoms in the chain. Branched chain alkanes, on the other hand, have one or more side chains branching off the main carbon chain. They have the same formula as straight chain alkanes, but the carbon atoms are arranged in a branched structure. The presence of these side chains results in a more complex and diverse range of compounds with different physical and chemical properties compared to straight chain alkanes. The naming convention for alkanes involves the use of prefixes to indicate the number of carbon atoms in the molecule and the presence of any branching. For example, methane (CH4) is the simplest alkane and ethane (C2H6) is a straight chain alkane with two carbon atoms, while isobutane (C4H10) is a branched chain alkane with four carbon atoms, including a branched side chain.

• Why are the differences between organic and inorganic compounds?

The main differences between organic and inorganic compounds lie in their chemical and physical properties, as well as their structures and sources. Chemically, organic compounds are characterized by the presence of carbon-hydrogen (C-H) bonds and carbon-carbon (C-C) bonds, which give them a unique ability to form complex structures and react with other compounds in a variety of ways. In contrast, inorganic compounds typically do not contain carbon-hydrogen bonds and are often characterized by ionic or covalent bonds between metals and nonmetals. Physically, organic compounds are generally volatile and have low melting and boiling points, due to the weak intermolecular forces between their molecules. Inorganic compounds, on the other hand, are often characterized by high melting and boiling points and are generally less volatile. Structurally, organic compounds can exist as simple molecules, such as methane or ethanol, or as complex macromolecules, such as proteins and DNA. Inorganic compounds can also form complex structures, but they are generally less diverse in terms of the types of bonds and structures they can form. Finally, organic compounds are primarily derived from living organisms, such as plants and animals, whereas inorganic compounds can be found in both living and non-living sources, including minerals, rocks, and water. Overall, the differences between organic and inorganic compounds reflect their unique chemical and physical properties, as well as their distinct sources and structures.

• How do we name cycloalkanes?

The naming of cycloalkanes follows the same basic principles as the naming of alkanes, with the addition of a prefix that indicates the presence of a ring. Here are the steps to name a cycloalkane: Count the number of carbon atoms in the ring. Cycloalkanes can have 3 or more carbon atoms in the ring. Number the carbons in the ring sequentially to assign locants (numbers) to substituents. Start with the carbon atom closest to a substituent if one is present. If there are multiple substituents, give priority to the substituent that appears first in alphabetical order. If there is only one substituent, use the prefix "cyclo-" before the name of the parent alkane. For example, cyclopropane and cyclobutane. If there are two or more substituents, use the prefixes "di-", "tri-", "tetra-", etc. to indicate the number of substituents. Use these prefixes before the name of the parent alkane, and arrange the substituents in alphabetical order. For example, 1,2-dimethylcyclohexane and 1,3,5-trimethylcyclohexane. If there are multiple substituents on the ring, use the numbering system to indicate the positions of the substituents. Number the ring in a way that gives the lowest possible locants to the substituents. For example, 1-methyl-3-ethylcyclopentane. If there are multiple possible ways to number the ring, choose the numbering system that gives the lowest possible locants to the substituents that have the highest priority according to the rules of substituent priority. In summary, naming cycloalkanes follows the same basic principles as naming alkanes, with the addition of a prefix that indicates the presence of a ring. The numbering of the carbons in the ring is important to assign locants to substituents and to indicate the positions of the substituents on the ring.

Examples of Organic Compounds

There are many examples of organic compounds, as organic chemistry is a very broad field. Here are some common examples of organic compounds: Alkanes: These are saturated hydrocarbons with the general formula CnH2n+2. Examples include methane, ethane, propane, butane, and pentane. Alkenes: These are unsaturated hydrocarbons with a carbon-carbon double bond. Examples include ethene, propene, butene, and pentene. Alkynes: These are unsaturated hydrocarbons with a carbon-carbon triple bond. Examples include ethyne, propyne, butyne, and pentyne. Aromatics: These are organic compounds with a ring-shaped structure containing alternating double bonds, such as benzene, toluene, and naphthalene. Alcohols: These are organic compounds that contain a hydroxyl (-OH) functional group. Examples include methanol, ethanol, propanol, and butanol. Aldehydes: These are organic compounds that contain a carbonyl group (-CHO) at the end of a carbon chain. Examples include formaldehyde, acetaldehyde, and benzaldehyde. Ketones: These are organic compounds that contain a carbonyl group (-C=O) in the middle of a carbon chain. Examples include acetone, propanone, and butanone. Carboxylic acids: These are organic compounds that contain a carboxyl group (-COOH). Examples include acetic acid, formic acid, and benzoic acid. Esters: These are organic compounds that are formed from a reaction between a carboxylic acid and an alcohol. Examples include methyl acetate, ethyl butyrate, and isopropyl benzoate. Amines: These are organic compounds that contain a nitrogen atom bonded to one or more carbon atoms. Examples include ethylamine, propylamine, and butylamine. These are just a few examples of the many types of organic compounds that exist. Organic compounds are used in a wide variety of applications, including fuels, pharmaceuticals, food additives, and materials science.

• How do we convert Lewis Structures to condensed structures and skeletal/line structures?

To convert Lewis structures to condensed structures, we simply write the symbols for the atoms in the molecule in the order in which they appear in the Lewis structure, followed by the number of atoms of each element in parentheses, and then the overall charge of the molecule outside the parentheses. To convert this to a condensed structure, we simply write "CH4", which indicates that there is one carbon atom and four hydrogen atoms in the molecule. To convert Lewis structures to skeletal or line structures, we start by identifying the longest continuous chain of carbon atoms in the molecule, which represents the backbone of the molecule. We then replace each carbon atom in the backbone with a single line segment and omit the hydrogen atoms bonded to them, unless they are attached to heteroatoms such as oxygen or nitrogen. We then add the necessary hydrogen atoms to satisfy the valence requirements of each atom in the molecule. To convert this to a skeletal structure, we identify the longest continuous chain of carbon atoms, which is a two-carbon chain. We replace each carbon atom with a single line segment and add the necessary hydrogen atoms to satisfy the valence requirements of each atom. The resulting skeletal structure is: CH3CH2OH This structure shows the connectivity of the atoms in the molecule and is often used to represent organic molecules in chemical reactions and other contexts.

Addition Reactions:

Types of Reactions: 1. Hydrogenation: Addition of hydrogen XY = H2 (in the presence of Palladium catalyst) 2. Halogenation: Addition of a halogen XY= Cl2, Br2 or I2 3. Hydrohalogenation: Addition of hydrogen halide XY = HCl (also HBr and HI) 4. Hydration: Addition of water XY= HOH in the presence of an acid (H2SO4)

If given the reactants in an addition reaction, can we write the products

Yes, if you are given the reactants in an addition reaction, you can write the products by understanding the nature of the reactants and the type of addition reaction that is taking place. The products of an addition reaction are determined by the way in which the atoms or groups of atoms in the reactants combine. For example, in the addition of hydrogen to an alkene, the double bond between the carbon atoms is broken and the hydrogen atoms are added to each carbon atom, resulting in the formation of an alkane. So, if you were given the reactant ethene (C2H4) and hydrogen (H2), you could write the product as ethane (C2H6), as shown below: C2H4 + H2 → C2H6 Similarly, if you were given the reactant propene (C3H6) and hydrogen chloride (HCl), you could write the product as 2-chloropropane (C3H7Cl), as shown below: C3H6 + HCl → C3H7Cl In addition to knowing the reactants, you may also need to consider factors such as stereochemistry, regiochemistry, and the mechanism of the reaction in order to accurately predict the products.

Examples of Organic Compounds

methane, propane, ethanol, caffeine acetylsalicylic acid

Introduction to Alkanes

• Hydrocarbons • C-H and C-C bonds only! • Molecular formula of all alkanes fits the general formula CnH2n+2

Cycloalkanes

• Hydrocarbons • C-H and C-C bonds only but arranged in a ring structure • Molecular formula of all cycloalkanes fits the general formula CnH2n

Introduction to Alkanes

• Hydrocarbons • C-H bonds only! • Molecular formula of all alkanes fits the general formula CnH2n+2

Isomers

• Isomers (constitutional): Same molecular formula but different connectivity of atoms

Why is it so important to study organic chemistry?

• Leads to drug development for the treatment of diseases and other conditions • Leads to development of more efficient processes for making materials needed in homes and industrial plants • Leads to an understanding of biochemical reactions that occur in the body • Helps us to understand the structure and hence the function of biological macromolecules

Hydrohalogenation

• Markovnikov's Rule: In the addition of HX to an alkene, the major product arises from the H attaching to the double-bond carbon that has the larger number of H atoms directly attached to it, and the X attaching to the carbon that has the smaller number of H atoms attached In short: H to C with more Hs and X (halogen) to C with more Carbons

Addition Reactions: General Form

• Most of the reactions of carbon-carbon multiple bonds are addition reactions. • A generalized reagent X-Y adds to the multiple bond to yield a saturated product that has only single bonds

Properties of Alkanes

• Nonpolar, insoluble in water but soluble in nonpolar organic solvents, less dense than water • Flammable, otherwise not very reactive • Mineral oil, petroleum jelly, and paraffin wax are mixtures of higher alkanes. All are harmless to body tissue and are used in numerous food and medical applications.

Representation and Naming Cycloalkanes

• Represented as polygons • Naming: • End: ane • Middle: based on the number of C atoms in the ring • Beginning: cyclo

Structure and Properties

• Rigid-very little rotation; in some cases no rotation at all • Ring strain leads to great reactivity; can react like an alkene • Properties similar to alkanes -lower molecular weight- gases and higher molecular weight-liquids and solids -non-polar; insoluble in water

Conformers

• Same molecular formula, same connectivity of atoms, differ by rotation of bonds-3D representations are different-Same compound!