Chemistry cheat Sheet - summaries of notes from the course PDF

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Chemistry cheat Sheet Alkanes- have single bonds, suffix ends in –ANE Alkenes- have double bonds, suffix ends in –ENE Alkynes – have triple bonds, suffixs ends in -YNE Saturated hydrocarbons are hydrocarbons that contain only single bonds between carbon atoms. They are the simplest class of hydrocarbons. They are called saturated because each carbon atom is bonded to as many hydrogen atoms as possible Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. Those with at least one carbon-to-carbon double bond are called alkenes and those with at least one carbon-to-carbon triple bond are called alkynes. Naming alkanes general formula for open chain alkenes = CH2  +2

Alkyl groups same prefix however suffix ends in YL e.g methyl, ethyl, propyl General formula for Alkyl groups is R= CH2 +1 Isomerism- because carbon can form four single bonds, alkanes with 4 or more carbon atoms can form isomers. Isomers are molecules that have the same molecular formula but have a different structural formula. Example: the molecular formula C4H10 can be related to two structural formulas, butane and isobutene

IUPAC Rules for naming Alkanes

1. 2. 3. 4. 5.

Identify the highest priority functional group ( a functional group is a portion of a molecule that is recognizable/ classified group of bound atoms) identify then name the longest continuous carbon chain number the chain so any branch or alkyl groups have the lowest possible number use prefixes (di, tri, tetra, etc) if two or more of the same alkyl group branches appear on the longest chain when several different groups are attached to the same parent compound, list groups in alphabetical order ( e.g ethyl before methyl )

Reactions of Alkanes

Free radical stability and Reactivity Carbon atoms are often classified based on the number of carbon atoms directly attached to them. Free radicals can be primary (1)[least stable], secondary (2) or tertiary (3) [most stable and the most easily formed radicals]

Cycloalkanes - Cycloalkanes are cyclic alkanes with the general formula CH2 -

The physical properties and the chemical reactivity of cycloalkanes are similar to their open chain counterparts with 2 exceptions

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Cyclopropane and cyclobutane have higher reactivity because their bonds are strained. The basis for the strain is the deviation of their bond angles from the normal tetrahedral carbon bond angle of 109.5

Naming cycloalkanes 1. Name the substituent 2. Name the parent cyclohexane When naming polysubstituted cycloalkanes 1. Number the ring (clockwise or counter clockwise) to give the substituted groups the lowest possible numbers 2. Name the groups and their locations 3. Name the parent cyclohexane

Module 2 Unsaturated hydrocarbons

IUPAC Rules for naming Alkenes 1. Identify the highest priority functional group 2. Identify then name the longest continuous carbon chain of atoms containing the C=C bond (or triple) 3. Name the parent alkane and change the –ane to –ene for alkenes or –yne for alkynes 4. Number the carbon chain to give the double bond (triple) bonded carbons the lowest numbers 5. Number the branched alkyl groups 6. Compounds with the two C=C are called dienes/ with three are called treins Geometric isomerism in Alkenes alkenes that have the same molecular formula and the same connectivity between atoms but different spatial orientation of the atoms are called geometric isomers or CIS/TRANS isomers

If a C=C carbon has two identical groups as shown here, then cis/trans isomerism will not occur in the alkene

Cycloalkenes -

Are cyclic compounds with a C=C bond in the ring

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The cyclo- in the name indicates the there is a double bond in the molecule

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The double bonds are given the lowest numbers

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Diene in the name indicates that each molecule contains two double bonds

Reactions of Alkenes

Module 5 Carboxylic Acids, Ester and & lipids

The sour tang in fruit juice comes from carboxylic acids. Carboxylic acids are organic compounds that contain the carboxyl functional group as shown here.

IUPAC rules for naming 1. Name the longest continuous carbon chain of carbon atoms containing the COOH group 2. The COOH carbon Is the #1 carbon atom because the carboxyl group is always at the beginning of the carbon chain 3. Drop the –e from the name of the parent alkane and add the suffix OIC ACID 4. Carboxyl group takes precedence over other groups in the naming 5. Sometimes Greek letters are used to in common names to locate groups attached to the molecules (alpha, beta, omega etc)

Physical properties of

Carboxylic Acids -

the solubility of carboxylic acids is determined by which of the two groups (the non-polar -COOH group) of the molecule is the most dominant in the chemical structure

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the relative high boiling points of carboxylic acids are due to intermolecular attractions resulting from the hydrogen bonding

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carboxylic acids are generally weak acids (only ionzed)

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the major types of carboxylic acids are; Unsaturated carboxylic acids Hydroxyl acids aromatic carboxylic acid Amino acids

As the number of carbons increases: -

melting point increases

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boiling point increases

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solubility in H2O

The solubility of carboxylic acids is determined by which of the two groups (the nonpolar R group or the polar –COOH group) of the molecule is the most dominant in the chemical structure. Carboxylic acids with: 

1–4 carbon atoms are water soluble

 

5–7 carbon atoms are slightly water soluble 8 and more carbon atoms are water insoluble

The relative high boiling points of carboxylic acids are due to intermolecular attractions resulting from hydrogen bonding, e. g. ethanoic acid bp 119 °C, ethanol bp 78 °C.

Carboxylic acids are generally weak acids; that is, they are only slightly ionized in water. Phenols are, in general, even weaker acids than carboxylic acids.

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Carboxylic acids in Biochemistry

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Carboxylic acids are released in the blood by the liver in an excessive amount during ketoacidosis

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Normal amounts of carboxylic acid can be controlled by blood buffers and by respiration rate and kidney function.

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L–Dopa (levodopa) is a carboxylic acid that is a derivative of dopamine and is used in

the treatment of Parkinson’s disease.

Classification of carboxylic acid

The major types of carboxylic acids are:    

Unsaturated carboxylic acids Aromatic carboxylic acids Hydroxy acids Amino acids

An unsaturated carboxylic acid contains one or more C=C bonds. The C=C bond affects the physical and chemical properties of the acid. For example, stearic acid, both contain 18 carbon atoms. Stearic acid has no C=C bonds and melts at 70 °C whereas oleic acid, , has one C=C bond and melts at 16 °C. Aromatic acids have a –COOH group bonded to a carbon in the aromatic ring. Benzoic acid and the three isomers of toluic acid are examples.

Hydroxy acids have hydroxyl (–OH) and carboxyl (–COOH) functional groups. Two important –hydroxy acids are lactic acid and salicylic acid. Lactic acid is found in sour milk as well as in muscle tissue after strenuous exercise. Salicyclic acid and its derivatives are found in analgesics like aspirin.

Amino

acids have a carboxyl group (-COOH) and an amino group (-

NH2). The –COOH group acts as an acid while the – NH2 acts as a base. Most amino acids in nature have the –NH2 in a-position as shown here.

Amino acid units are the building blocks of proteins. Approximately 20 amino acids are biologically significant. Preparation of Carboxylic Acids Carboxylic acids can be prepared by various methods. - oxidation of primary alcohols or aldehydes

- Primary alcohols are oxidised to carboxylic acids

Primary alcohols like benzyl alcohol can also be oxidized to a carboxylic acid

Aldehydes also oxidize to carboxylic acids

Chemical Properties of carboxylic acid - the principal reaction of ester is hydrolysis – acid-catalysed or

- base-promoted ( alkaline hydrolysis/saponification)

Carboxylic acids undergo two broad classes of reactions which are acid based reactions and substitutions reaction 1. Acid- base reactions occur because the –COOH group can act as a proton donor 2. The C=O on the –COOH group serves as a site for substation reactions Acid-base Properties Low molar-mass carboxylic acids release H+ ions in solutions and as a result have the following properties unique to acids in general - Sour taste - Blue litmus paper changes to red in an acidic solution - Forms solutions with a pH greater less than 7 - Reacts with bases in neutralisation reactions -

Ester Formation Esters can be prepared by a reacting a carboxylic acid and an alcohol or a phenol in the presence of a strong acid catalyst.

The specific reaction of formic acid and ethanol is below

Carboxylic Acids Summary - carboxylic acids contain the carboxyl group - The IUPAC naming of carboxylic acids follows similar process to that used for other orhganic molecules - Many carboxylic are known by common names. Each common name generally refers to a natural source for the carboxylic acid. - The polar carboxyl group causes the small carboxylic acids to be water soluble

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Carboxyl groups can hydrogen bond to each other at two places. This strong non-covalent bonding causes high boiling points for carboxylic acids Carboxylic acids are weak acids Strong oxidizing agents will convert aldehydes and pimrary alcohols to carboxylic acids Carboxylic acids have a sour taste, affect pH indicators, form water solutions with a ph less than 7 and undergo neutralisation Carboxylic acids react with bases to form salts

Nomenclature of Esters 1. Name the alkoxy alkyl group. This is the alcohol portion of the molecule. 2. Name the carboxylic acid portion of the molecule. Change the –ic in the name of the acid to –ate. 3. The alcohol portion is named first followed by the name of the acid portion.

The IUPAC name for this ester is methyl ethanoate. The common name is methyl acetate.

The ester formed by the reaction of propanoic acid and methanol is methyl propanoate. The common name is methyl propionate

Occurrence and Physical Properties of Esters

Low molar mass esters are volatile nonpolar liquids at room temperature. For example,

esters such as ethyl acetate, butyl acetate, and isoamyl acetate are used extensively in paints, varnishes, and lacquers. Low– and intermediate–molar–mass esters have characteristic fragrant or fruity odours. The difference in properties between an acid and its esters is

remarkable.

- High molar mass esters are nonpolar solids at room temperature. - Many of these esters are waxes. Carnauba wax is an ester that can have a 28–carbon fatty acid chain and a 34–carbon alcohol chain. - High molar mass esters are used in furniture and automobile wax preparations. Polyesters: Condensation Polymers

A polyester is a polymer formed between an alcohol monomer and a carboxylic acid monomer. Polyesters are classified as condensation polymers. An example of a general polymerization reaction to produce a polyester is shown here.

This is a polymerization reaction that produces the polyethylene terephthalate (PETE) polyester. Polyethylene terephthalate is a common polyester found in Mylar films and soft drink bottles.

This is the plastic recycle code for polethylene terephthalate. The principal reaction of esters is hydrolysis. Ester hydrolysis is either acid–catalysed (acid hydrolysis) or base–promoted (alkaline hydrolysis/saponification). An ester hydrolysed in the presence of an acid catalyst forms an alcohol and a carboxylic acid. The acid is a catalyst so it isn’t consumed during the reaction.

The ester hydrolysis in the presence of a strong base to form an alcohol and a salt is called saponification.

The carboxylic acid may be obtained by reacting the salt obtained from the hydrolysis with a strong acid. Notice that in saponification, the base is a reactant, not a catalyst.

Glycerol Esters

Esters of glycerol (glycerol esters) are known as triacylglycerols and triglycerides. Fats and oils are triacylglycerols. Fats originating from animal sources are solids at room temperature because they have a higher percentage of saturated fatty acid derivatives in their triacylglycerol structure. Oils originating from plant sources are liquids at room temperature because they have a higher percentage of unsaturated fatty acid derivatives in their triacylglycerol structure.

Some common unsaturated fatty acid derivatives found in oils include the corresponding parent fatty acids oleic acid, linoleic acid, and linolenic acid.

Triacylglycerols undergo two basic types of reactions: Hydrogenation - Acid and basic hydrolysis. Hydrogenation of Glycerides Oils can be partially hydrogenated using a metal catalyst and hydrogen gas to obtain a solid like the shortening found in Crisco.

During partial hydrogenation some of the cis bonds change to trans bonds which is the basis for the term “trans fat”. Research has shown these unnatural fats to be unhealthy and to increase the risk of heart disease. Acid Hydrolysis Fatty acids can be prepared by hydrolysing triacylglycerols with either enzymes or mineral acid catalysts.

Soaps are salts of long–chain fatty acids that are prepared by reacting fat or oil with sodium hydroxide The hydrocarbon tail of the carboxylate ion is nonpolar and dissolves the nonpolar grease. The hydrocarbon tail is hydrophobic (i.e. water–fearing). The polar head of the carboxylate ion allows the ion to remain soluble in water which is also polar. The polar head is hydrophilic (i.e. water–loving).

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The cleansing action of soaps in hard water is limited because hard water contains ions that react with carboxylate ions to form insoluble salts ( soap scum)

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Soaps are also ineffective in acidic solutions because insoluble fatty acids are formed.

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Synthetic detergents are synthetic organic products that act as cleansing agents. These synthetic detergents are effective in soft water and hard water. Two examples are shown below. Summary of esters:

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An ester is formed when an alcohol or phenol substitutes for the carboxylic acid hydroxyl group.

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Esters are named as alcohol derivatives of carboxylic acids.

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Condensation polymers are produced when monomers combine with the loss of a small molecule. Polyesters are formed when alcohol monomers react with carboxylic acid monomers with the loss of water.

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The most important reaction of esters is hydrolysis.

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Fats and oils are esters of glycerol and long–chain carboxylic acids (fatty acids).

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A triacylglycerol or triglyceride is a glycerol that has been esterified with three fatty acids molecules.

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Fats are solids at room temperature, while oils are liquids.

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Triacylglycerols are the principal energy–storage molecules in the human body.

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Hydrogenation of unsaturated fatty acids results in the addition of hydrogen to carbon–carbon double bonds.

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Triacylglycerols can be hydrolysed in acid to form fatty acids and glycerol or in base to form soaps and glycerol.

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Soaps are salts of long–chain fatty acids.

Lipids: Hydrophobic Molecules Polar bears have a large reserve of lipids. A layer of fat under the penguin’s skin serves as insulation against extreme cold. Lipids are water–insoluble substances that have several important biological functions. Lipids interact weakly with water molecules because they are composed primarily of nonpolar alkyl groups. Lipids are classified as hydrophobic (“water fearing”) to designate their inability to interact effectively with water or their strong tendency to move away from water. Fatty acids are common components of lipids

Classification of Lipids

Lipids molecules are relatively large and nonpolar. Yet, within this broad description, lipid structures vary markedly. Lipids can be classified in four categories which recognize major structural similarities. 

Simple lipids

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Compound lipids

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Steroids

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Miscellaneous lipids

Simple Lipids

The simple lipids include fats, oils, and waxes. These simple lipids are derivatives of lipid–like substances call fatty acids. Fatty acids are long–chain carboxylic acids (generally greater than about 12 carbons) that have no solubility in water. The hydrophilic –COOH group is referred to as a polar head and the hydrophobic hydrocarbon portion is referred to as a nonpolar tail. Fats and waxes are solids due to a higher composition of saturated fatty acids while oils are liquids due to a higher composition of unsaturated fatty acids. Table 28.1 lists properties of saturated and unsaturated fatty acids separately. Notice how unsaturated fatty acids generally have lower melting points than saturated fatty acids. Unsaturated fatty acids exist as cis and trans isomers. The cis isomer is more prevalent in nature. The cis and trans isomers of oleic acid are shown below. Oleic acid is an unsaturated fatty acid. The cis isomer has a bent structure which prevents close stacking resulting in a compound that resists solidification.

Eicosanoids are hormones and coordinate various cellular responses. Some are involved with blood clotting as they can cause platelet aggregation while others trigger an increase in body temperature. Some eicosanoids coordinate HCl and mucous secretion by the stomach lining and constriction of the bronchial tubes in the lungs. Some eicosanoids stimulate and attract white cells, while other eicosanoids cause the white cells to disperse. Eicosanoids can also cause vasodilation as well as vasoconstriction. Many drugs control one or more of the physiological effects produced by the eicosanoids. For example, aspirin is a nonsteroidal anti–inflammatory drug that blocks the oxidation of arachidonic acid which in turn prevents the formation of prostaglandins and thromboxanes

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Fats and oils are triester derivatives of glycerol and three fatty acid molecules as shown below. Because there are three ester groups per glycerol, these lipids are called triacylglycerols or triglycerides.

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have carbon chains with 14–18 carbon atoms.

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Triglycerides are prepared by the reaction of a glycerol molecule and three fatty acid molecules.

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fatty acid molecules can be saturated or unsaturated.

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Compound Lipids

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There are three broad categories of compound lipids.

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Phospholipids Sphingolipids Glycolipids

Phospholipids – the phospholipids are a group of compounds that yield one or more fatty acid molecules, a phosphate group, and usually a nitrogenous base upon hydrolysis. In contrast to the triacylglycerols, phospholipids have a hydrophilic end that interacts with water.

Sphin...