Alcohols, Thiols, Ethers and Amines · identify the functional groups alcohol, phenol, thiol, ether, and amine on organic chemical structures · provide. In this reaction a primary alcohol is heated with an acid catalyst (usually sulfuric acid). A molecule of water is lost and the ether is formed from two. IN THIS CHAPTER, we study the physical and chemical properties of alcohols and ethers, two classes of oxygen-containing compounds we have seen as products. NAZRI KHAN FOREX BROKER

They are indicators of functional groups, and in that role can have a strong influence on the properties of these substances. Alcohol names are related closely to the names of the hydrocarbons they resemble, with key modifications. For instance, the molecule above without the hydroxy group would be named cyclopentane.

The alcohol is named cyclopentanol. When this is the case, provide a number that indicates the number of the carbon in the parent chain where the oxygen is attached. For cyclopentanol this is not necessary because there are not distinct carbons that are numbered. But in this example a number is required: Numbering from either end of the parent chain 5 carbons would identify carbon 3 as the point where the hydroxy -OH group connects to the chain.

So the name of this alcohol is 3-pentanol. You may also see the more technically correct according to IUPAC pentaneol, but this form of nomenclature has been slow to catch on in practice. As with branches on an alkane, the number is assigned from whichever end of the parent chain produces the lowest possible number for the alcohol. Compounds containing this structure are named phenols, after the name of the substance below, which is the simplest of these aromatic alcohols, and is named phenol: There are of course variations that make for extra challenge: branched hydrocarbon structures with alcohol groups and molecules with more than one functional group, for instance.

Those issue can be dealt with later, once you have more experience. Exercise 5. The group -SH can be referred to as a thiol group. Occasionally the common name mercaptan is still used to describe members of this organic family. Naming thiols involves a modification of the name of the corresponding hydrocarbon. These names will seem odd as you first learn them and you might find pronunciation unclear or difficult. That is normal. The names are designed to first convey structural information and only secondarily to be easy to speak.

In this case, the oxygen is incorporated into a chain of carbons, so that it has two single-bond connections to two separate carbons. IUPAC rules for naming ethers involve naming one side of the ether as if it were a substituent group on the other carbons. This is somewhat complicated. Thiols are more nucleophilic than alcohols, and thiolates are more nucleophilic than alkoxides.

Since nucleophilicity is measured by reaction rate , that means that these sulfur nucleophiles tend to react faster with typical electrophiles like alkyl halides than their oxygen-based cousins. This trend continues as we descend a column of the periodic table, so in general, nucleophilicity increases in this direction as well i. RSe— is even more nucleophilic than RS—. This process resembles the Williamson to a tee. First, a strong base deprotonates the thiol we use NaH here, but many other bases could also be used.

Secondly, we add an alkyl halide, and an SN2 reaction results in formation of S-C and breakage of C-Br with inversion of stereochemistry. Since it comes up so much in exams, the intramolecular version is important to note. Oxidation In previous posts we saw that primary alcohols are oxidized to aldehydes and secondary alcohols are oxidized to ketones.

Thiols can be oxidized to disulfides through treatment with a mild oxidant like iodine I2. A second oxidation pathway involves oxidation of sulfides to sulfoxides and sulfones through treatment with oxidants such as O3 ozone and peroxyacids such as m-chloroperoxybenzoic acid mCPBA.

Note that sulfur can exceed an octet of electrons whereas oxygen cannot. The oxidation of thiols to disulfides has important biological implications. The important amino acid cysteine contains a thiol group and disulfide bonds are responsible for the tertiary structures of proteins. Intermolecular forces are not very strong! Secondly, due to the smaller dipole electronegativity difference of the S-H as opposed to O-H, there is less partial negative charge on sulfur and therefore less electrostatic attraction between S and the H of various acids.

A better way of converting sulfur to a good leaving group is by treating it with Lewis acids such as Hg OAc 2. For example, treatment of alkenes with OsO4 results in vicinal diols. Nor is there a sulfur equivalent to the formation of epoxides from alkenes with, say, the sulfur equivalent of mCPBA.

FOREX TRADER LIFE

Washing the affected part with a basic solution soap for example will help solubilize the urushiol and remove it from the skin. Alcohol acidity can also be increased by inductive electron withdrawal due to the presence of electronegative atoms linked through sigma bonds just as we discussed earlier in the case of carboxylic acids: for example CF3OH is more acidic than CH3OH. We might also predict the effects relative to acidities of amines and thiols in terms of resonance and inductive stabilization, but, in fact, most of their chemistry is not associated with acidity and we will not dwell on this idea here.

For functional groups that contain nucleophilic centers from the same row of the periodic table, the trends in nucleophilicity parallel Bronsted basicity: amines are more nucleophilic and basic than alcohols. However, in functional groups that contain nucleophilic centers from the same group of the periodic table nucleophilicity increases down the group, while basicity decreases , thiols are more nucleophilic than alcohols.

Both amines and thiols are very nucleophilic. All three groups participate in nucleophilic substitutions as discussed in Chapters 1 and 4. Examples of these kinds of nucleophilic substitutions are the reactions of alcohols, thiols, and amines with alkyl halides to give the corresponding ethers, sulfides, and secondary, tertiary or quaternary amines.

Alcohols are not as nucleophilic as thiols and amines, and therefore typically the corresponding alkoxide must be used because it is more reactive , for the synthesis of ethers. In the case of amines, the nitrogen can react several times with the electrophile alkyl halide , and in practice it is difficult to stop the reaction at any intermediate step in the laboratory. Amines typically react with electrophiles to give poly-alkylated amines O, S, and N as leaving groups: Recall that a good leaving group should be able to accept in a stable form the pair of electrons from the bond that breaks.

Typically, good leaving groups are weak bases. For this reason, hydroxide —OH and amide —NH2 are unlikely to be produced during a nucleophilic substitution reaction. However, as noted earlier, alcohols can be converted into good leaving groups by protonation, which results in H2O as the leaving group. Alcohols can also be modified or derivatized to produce better leaving groups. This is particularly useful when we need to carry out a reaction that is sensitive to acidic conditions when the method we have used earlier protonation of the OH cannot be used.

The most common derivative used to make the OH group into a good leaving group is the Tosyl group para-toluenesulphonate. It can be formed by reacting an alcohol with p-toluenesulfonylchloride TosCl in the presence of a base such as pyridine that acts to remove the HCl that is produced. We can consider the derivatization reaction as mechanistically similar to other nucleophilic substitutions we have considered, except that it takes place at an S instead of a C.

The resulting OTos group is a very good leaving group, making the molecule reactive to nucleophilic substitution reactions. In effect, we have changed the leaving group from —OH, which is a relatively strong base, to —OTos which is a very weak base—it is the organic equivalent of sulfate, the conjugate base of sulfuric acid.

The negative charge on —OTos becomes delocalized to the other oxygens bound to the S, thereby stabilizing the base. In a similar manner, sulfides can be transformed into leaving groups, most commonly through the methylation of the sulfide, which produces a powerful reagent that can be used to methylate other species.

Recall that in earlier discussions we used the term reduction to mean the addition of hydrogen and oxidation to mean the addition of oxygen, rather than calculating changes in oxidation numbers decrease for reduction, increase for oxidation. The reason is because oxidation numbers in organic compounds can be hard to calculate and apply [3]. In this section, we consider how alcohols can be oxidized to give aldehydes, ketones, or carboxylic acids.

In general, we consider a carbon compound to be oxidized when the number of bonds between the C and electronegative atoms often, but not always, O is increased. For example, a primary alcohol can be oxidized which we will denote by O for the time being to an aldehyde; depending upon the reagent used, the reaction can proceed through a second step to produce the corresponding carboxylic acid.

At each step, the oxidation level of the carbon is increasing. Starting with a secondary alcohol, the product of an oxidation reaction is the corresponding ketone, but tertiary alcohols do not give useful products and may simply lead to degradation C—C bond breaking. Generally, it is not possible to oxidize a secondary carbon beyond the ketone level without breaking carbon-carbon bonds, and similarly, tertiary alcohols cannot be oxidized under normal circumstances. Typical oxidizing reagents include transition metals in high-oxidation states that is able to accept [bond to] O atom.

For example, chromium VI in the form of chromium trioxide CrO3 or sodium dichromate Na2Cr2O7 , when in concentrated H2SO4, are both powerful oxidizing agents and both will oxidize a primary alcohol through both steps, that is, all the way to the carboxylic acid form.

The general mechanism of oxidation is shown below, note electrons leave the alcohol and end up on the Cr, reducing its oxidation state from 6 to 4, and the alcohol carbon ends up oxidized. Primary alcohols can be selectively oxidized to aldehydes with PCC One problematic aspect of such oxidizing reagents is that they contain highly toxic and carcinogenic Cr VI in one form or another.

Such materials oxidize a range of biomolecules such as vitamin C ascorbic acid and some thiols such as the amino acid cysteine. To avoid using such toxic chemicals, there has been increasing in what has come to be known as green chemistry [4]. One of the tenets of green chemistry is to minimize the use of toxic reagents such as chromium compounds. In contrast, with thiols the oxidation site is often at the sulfur.

For example, many oxidizing agents even molecular oxygen in air oxidize thiols to disulfides. The disulfide bond is relatively weak, that is, requires less energy to break about half the strength of a typical C-C or C-H bond. We might also predict the effects relative to acidities of amines and thiols in terms of resonance and inductive stabilization, but, in fact, most of their chemistry is not associated with acidity and we will not dwell on this idea here.

For functional groups that contain nucleophilic centers from the same row of the periodic table, the trends in nucleophilicity parallel Bronsted basicity: amines are more nucleophilic and basic than alcohols. However, in functional groups that contain nucleophilic centers from the same group of the periodic table nucleophilicity increases down the group, while basicity decreases , thiols are more nucleophilic than alcohols. Both amines and thiols are very nucleophilic.

All three groups participate in nucleophilic substitutions as discussed in Chapters 1 and 4. Examples of these kinds of nucleophilic substitutions are the reactions of alcohols, thiols, and amines with alkyl halides to give the corresponding ethers, sulfides, and secondary, tertiary or quaternary amines. Alcohols are not as nucleophilic as thiols and amines, and therefore typically the corresponding alkoxide must be used because it is more reactive , for the synthesis of ethers.

In the case of amines, the nitrogen can react several times with the electrophile alkyl halide , and in practice it is difficult to stop the reaction at any intermediate step in the laboratory. Amines typically react with electrophiles to give poly-alkylated amines O, S, and N as leaving groups: Recall that a good leaving group should be able to accept in a stable form the pair of electrons from the bond that breaks.

Typically, good leaving groups are weak bases. For this reason, hydroxide —OH and amide —NH2 are unlikely to be produced during a nucleophilic substitution reaction. However, as noted earlier, alcohols can be converted into good leaving groups by protonation, which results in H2O as the leaving group. Alcohols can also be modified or derivatized to produce better leaving groups. This is particularly useful when we need to carry out a reaction that is sensitive to acidic conditions when the method we have used earlier protonation of the OH cannot be used.

The most common derivative used to make the OH group into a good leaving group is the Tosyl group para-toluenesulphonate. It can be formed by reacting an alcohol with p-toluenesulfonylchloride TosCl in the presence of a base such as pyridine that acts to remove the HCl that is produced. We can consider the derivatization reaction as mechanistically similar to other nucleophilic substitutions we have considered, except that it takes place at an S instead of a C.

The resulting OTos group is a very good leaving group, making the molecule reactive to nucleophilic substitution reactions. In effect, we have changed the leaving group from —OH, which is a relatively strong base, to —OTos which is a very weak base—it is the organic equivalent of sulfate, the conjugate base of sulfuric acid.

The negative charge on —OTos becomes delocalized to the other oxygens bound to the S, thereby stabilizing the base. In a similar manner, sulfides can be transformed into leaving groups, most commonly through the methylation of the sulfide, which produces a powerful reagent that can be used to methylate other species.

Recall that in earlier discussions we used the term reduction to mean the addition of hydrogen and oxidation to mean the addition of oxygen, rather than calculating changes in oxidation numbers decrease for reduction, increase for oxidation.

The reason is because oxidation numbers in organic compounds can be hard to calculate and apply [3]. In this section, we consider how alcohols can be oxidized to give aldehydes, ketones, or carboxylic acids. In general, we consider a carbon compound to be oxidized when the number of bonds between the C and electronegative atoms often, but not always, O is increased.

For example, a primary alcohol can be oxidized which we will denote by O for the time being to an aldehyde; depending upon the reagent used, the reaction can proceed through a second step to produce the corresponding carboxylic acid. At each step, the oxidation level of the carbon is increasing. Starting with a secondary alcohol, the product of an oxidation reaction is the corresponding ketone, but tertiary alcohols do not give useful products and may simply lead to degradation C—C bond breaking.

Generally, it is not possible to oxidize a secondary carbon beyond the ketone level without breaking carbon-carbon bonds, and similarly, tertiary alcohols cannot be oxidized under normal circumstances. Typical oxidizing reagents include transition metals in high-oxidation states that is able to accept [bond to] O atom.

For example, chromium VI in the form of chromium trioxide CrO3 or sodium dichromate Na2Cr2O7 , when in concentrated H2SO4, are both powerful oxidizing agents and both will oxidize a primary alcohol through both steps, that is, all the way to the carboxylic acid form.

The general mechanism of oxidation is shown below, note electrons leave the alcohol and end up on the Cr, reducing its oxidation state from 6 to 4, and the alcohol carbon ends up oxidized. Primary alcohols can be selectively oxidized to aldehydes with PCC One problematic aspect of such oxidizing reagents is that they contain highly toxic and carcinogenic Cr VI in one form or another.

Such materials oxidize a range of biomolecules such as vitamin C ascorbic acid and some thiols such as the amino acid cysteine. To avoid using such toxic chemicals, there has been increasing in what has come to be known as green chemistry [4]. One of the tenets of green chemistry is to minimize the use of toxic reagents such as chromium compounds.

In contrast, with thiols the oxidation site is often at the sulfur. For example, many oxidizing agents even molecular oxygen in air oxidize thiols to disulfides. The disulfide bond is relatively weak, that is, requires less energy to break about half the strength of a typical C-C or C-H bond.

These disulfide crosslinks between cysteine moieties in polypeptides and proteins often serve to stabilize the 3D structure of proteins. Sulfides R-S-R are also susceptible to oxidation, which can lead to the formation of a sulfoxide, which can be further oxidized to form a sulfone.

Alcohols ethers and thiols yankees at tigers

(10.9) Alcohols, Phenols, and Thiols

GURBAKSH CHAHAL CRYPTOCURRENCY

In the case of amines, the nitrogen can react several times with the electrophile alkyl halide , and in practice it is difficult to stop the reaction at any intermediate step in the laboratory. Amines typically react with electrophiles to give poly-alkylated amines O, S, and N as leaving groups: Recall that a good leaving group should be able to accept in a stable form the pair of electrons from the bond that breaks.

Typically, good leaving groups are weak bases. For this reason, hydroxide —OH and amide —NH2 are unlikely to be produced during a nucleophilic substitution reaction. However, as noted earlier, alcohols can be converted into good leaving groups by protonation, which results in H2O as the leaving group. Alcohols can also be modified or derivatized to produce better leaving groups.

This is particularly useful when we need to carry out a reaction that is sensitive to acidic conditions when the method we have used earlier protonation of the OH cannot be used. The most common derivative used to make the OH group into a good leaving group is the Tosyl group para-toluenesulphonate. It can be formed by reacting an alcohol with p-toluenesulfonylchloride TosCl in the presence of a base such as pyridine that acts to remove the HCl that is produced.

We can consider the derivatization reaction as mechanistically similar to other nucleophilic substitutions we have considered, except that it takes place at an S instead of a C. The resulting OTos group is a very good leaving group, making the molecule reactive to nucleophilic substitution reactions. In effect, we have changed the leaving group from —OH, which is a relatively strong base, to —OTos which is a very weak base—it is the organic equivalent of sulfate, the conjugate base of sulfuric acid.

The negative charge on —OTos becomes delocalized to the other oxygens bound to the S, thereby stabilizing the base. In a similar manner, sulfides can be transformed into leaving groups, most commonly through the methylation of the sulfide, which produces a powerful reagent that can be used to methylate other species. Recall that in earlier discussions we used the term reduction to mean the addition of hydrogen and oxidation to mean the addition of oxygen, rather than calculating changes in oxidation numbers decrease for reduction, increase for oxidation.

The reason is because oxidation numbers in organic compounds can be hard to calculate and apply [3]. In this section, we consider how alcohols can be oxidized to give aldehydes, ketones, or carboxylic acids. In general, we consider a carbon compound to be oxidized when the number of bonds between the C and electronegative atoms often, but not always, O is increased.

For example, a primary alcohol can be oxidized which we will denote by O for the time being to an aldehyde; depending upon the reagent used, the reaction can proceed through a second step to produce the corresponding carboxylic acid. At each step, the oxidation level of the carbon is increasing. Starting with a secondary alcohol, the product of an oxidation reaction is the corresponding ketone, but tertiary alcohols do not give useful products and may simply lead to degradation C—C bond breaking.

Generally, it is not possible to oxidize a secondary carbon beyond the ketone level without breaking carbon-carbon bonds, and similarly, tertiary alcohols cannot be oxidized under normal circumstances. Typical oxidizing reagents include transition metals in high-oxidation states that is able to accept [bond to] O atom. For example, chromium VI in the form of chromium trioxide CrO3 or sodium dichromate Na2Cr2O7 , when in concentrated H2SO4, are both powerful oxidizing agents and both will oxidize a primary alcohol through both steps, that is, all the way to the carboxylic acid form.

The general mechanism of oxidation is shown below, note electrons leave the alcohol and end up on the Cr, reducing its oxidation state from 6 to 4, and the alcohol carbon ends up oxidized. Primary alcohols can be selectively oxidized to aldehydes with PCC One problematic aspect of such oxidizing reagents is that they contain highly toxic and carcinogenic Cr VI in one form or another.

Such materials oxidize a range of biomolecules such as vitamin C ascorbic acid and some thiols such as the amino acid cysteine. To avoid using such toxic chemicals, there has been increasing in what has come to be known as green chemistry [4]. One of the tenets of green chemistry is to minimize the use of toxic reagents such as chromium compounds.

In contrast, with thiols the oxidation site is often at the sulfur. For example, many oxidizing agents even molecular oxygen in air oxidize thiols to disulfides. The disulfide bond is relatively weak, that is, requires less energy to break about half the strength of a typical C-C or C-H bond. These disulfide crosslinks between cysteine moieties in polypeptides and proteins often serve to stabilize the 3D structure of proteins. Sulfides R-S-R are also susceptible to oxidation, which can lead to the formation of a sulfoxide, which can be further oxidized to form a sulfone.

Preparation of alcohols We have already seen several methods by which alcohols can be produced, mostly in Chapter 5. We have also seen, under certain conditions, that alcohols can be produced by nucleophilic substitution.

Both SN1 and SN2 reactions can produce alcohols, and now would be a good time to review all of these reactions covered in Chapters 1, 3, 4 and 5. A reaction that we have not yet encountered is the reduction of carbonyl compounds. For example, a ketone such as acetone can be reduced through a reaction with sodium borohydride NaBH4 or lithium aluminum hydride LiAlH4 [7] ; both of these molecules can deliver hydride H— to the partially positive carbon of the carbonyl.

Sodium borohydride NaBH4 is generally the reagent of choice as it is less reactive and the reaction can be carried in an open flask, whereas LiAlH4 typically must be used with solvents that do not contain water and under a dry atmosphere. The intermediate R—O—BH3 complex is destroyed by adding aqueous acid to give the final alcohol product. Typically, good leaving groups are weak bases.

For this reason, hydroxide —OH and amide —NH2 are unlikely to be produced during a nucleophilic substitution reaction. However, as noted earlier, alcohols can be converted into good leaving groups by protonation, which results in H2O as the leaving group.

Alcohols can also be modified or derivatized to produce better leaving groups. This is particularly useful when we need to carry out a reaction that is sensitive to acidic conditions when the method we have used earlier protonation of the OH cannot be used. The most common derivative used to make the OH group into a good leaving group is the Tosyl group para-toluenesulphonate.

It can be formed by reacting an alcohol with p-toluenesulfonylchloride TosCl in the presence of a base such as pyridine that acts to remove the HCl that is produced. We can consider the derivatization reaction as mechanistically similar to other nucleophilic substitutions we have considered, except that it takes place at an S instead of a C. The resulting OTos group is a very good leaving group, making the molecule reactive to nucleophilic substitution reactions.

In effect, we have changed the leaving group from —OH, which is a relatively strong base, to —OTos which is a very weak base—it is the organic equivalent of sulfate, the conjugate base of sulfuric acid. The negative charge on —OTos becomes delocalized to the other oxygens bound to the S, thereby stabilizing the base.

In a similar manner, sulfides can be transformed into leaving groups, most commonly through the methylation of the sulfide, which produces a powerful reagent that can be used to methylate other species. Recall that in earlier discussions we used the term reduction to mean the addition of hydrogen and oxidation to mean the addition of oxygen, rather than calculating changes in oxidation numbers decrease for reduction, increase for oxidation.

The reason is because oxidation numbers in organic compounds can be hard to calculate and apply [3]. In this section, we consider how alcohols can be oxidized to give aldehydes, ketones, or carboxylic acids. In general, we consider a carbon compound to be oxidized when the number of bonds between the C and electronegative atoms often, but not always, O is increased.

For example, a primary alcohol can be oxidized which we will denote by O for the time being to an aldehyde; depending upon the reagent used, the reaction can proceed through a second step to produce the corresponding carboxylic acid. At each step, the oxidation level of the carbon is increasing. Starting with a secondary alcohol, the product of an oxidation reaction is the corresponding ketone, but tertiary alcohols do not give useful products and may simply lead to degradation C—C bond breaking.

Generally, it is not possible to oxidize a secondary carbon beyond the ketone level without breaking carbon-carbon bonds, and similarly, tertiary alcohols cannot be oxidized under normal circumstances. Typical oxidizing reagents include transition metals in high-oxidation states that is able to accept [bond to] O atom.

For example, chromium VI in the form of chromium trioxide CrO3 or sodium dichromate Na2Cr2O7 , when in concentrated H2SO4, are both powerful oxidizing agents and both will oxidize a primary alcohol through both steps, that is, all the way to the carboxylic acid form. The general mechanism of oxidation is shown below, note electrons leave the alcohol and end up on the Cr, reducing its oxidation state from 6 to 4, and the alcohol carbon ends up oxidized. Primary alcohols can be selectively oxidized to aldehydes with PCC One problematic aspect of such oxidizing reagents is that they contain highly toxic and carcinogenic Cr VI in one form or another.

Such materials oxidize a range of biomolecules such as vitamin C ascorbic acid and some thiols such as the amino acid cysteine. To avoid using such toxic chemicals, there has been increasing in what has come to be known as green chemistry [4].

One of the tenets of green chemistry is to minimize the use of toxic reagents such as chromium compounds. In contrast, with thiols the oxidation site is often at the sulfur. For example, many oxidizing agents even molecular oxygen in air oxidize thiols to disulfides. The disulfide bond is relatively weak, that is, requires less energy to break about half the strength of a typical C-C or C-H bond.

These disulfide crosslinks between cysteine moieties in polypeptides and proteins often serve to stabilize the 3D structure of proteins. Sulfides R-S-R are also susceptible to oxidation, which can lead to the formation of a sulfoxide, which can be further oxidized to form a sulfone. Preparation of alcohols We have already seen several methods by which alcohols can be produced, mostly in Chapter 5.

We have also seen, under certain conditions, that alcohols can be produced by nucleophilic substitution. Both SN1 and SN2 reactions can produce alcohols, and now would be a good time to review all of these reactions covered in Chapters 1, 3, 4 and 5. A reaction that we have not yet encountered is the reduction of carbonyl compounds. For example, a ketone such as acetone can be reduced through a reaction with sodium borohydride NaBH4 or lithium aluminum hydride LiAlH4 [7] ; both of these molecules can deliver hydride H— to the partially positive carbon of the carbonyl.

Sodium borohydride NaBH4 is generally the reagent of choice as it is less reactive and the reaction can be carried in an open flask, whereas LiAlH4 typically must be used with solvents that do not contain water and under a dry atmosphere.

The intermediate R—O—BH3 complex is destroyed by adding aqueous acid to give the final alcohol product. Reactions where hydride is delivered to a carbonyl are similar to a reaction found in biological systems. NADH Nicotinamide Adenine Dinucleotide Hydride is an unstable intermediate generated through a number of metabolic processes such as fermentation , while not as reactive as NaBH4, and like, essentially, all biological reactions requires a catalyst an enzyme to bring about the reduction of carbonyls; but the mechanism is similar.

Alcohols ethers and thiols investing in paramount pictures studios

CHM 203 Ch 14: Ethers and Epoxides, Thiols and Sulfides

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Introductory Organic Chemistry 5.

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