Mod+3+Reading+Guide

__**Reading Guide for Module 3**__ The main point of Module 3 is understanding how hydrocarbons are named, built, and describing the various functional groups and the effect these have upon a compound's properties.

__11.3: Alkanes with Substituents__ ->Summary: Branches from the carbon chains of large compounds are called substituents. Isomers are two compounds that have identical composition, but whose atoms are arranged differently. We name aklanes, cycloalkanes, and haloalkanes in a sequential fashion that allows a chemist to reproduce the structure of the compound including all of its substituents from only the name of the compound or to name the compound from seeing the compound's structure.

->Struggling Topic 1: How do you determine the relative placement of substituents in a compound like 2,4-dibromo-2,4dimethyl hexane? It would seem to me like the methyl group on carbon 2 could be on the same side of the carbon chain as the bromine atom on carbon 4, or it could be on the same side as the other methyl group on carbon 4. How do we determine the difference? Is this a cis/trans problem, and if so, does this information get placed in the compound's name?

->Struggling Topic 2: Compounds that can be made in two distinctly different arrangements of atoms are isomers. Is it important when there is minor variance in the orientation of substituents, or does this simply occur by a compound's orientation in space? For example, a 2,4-dimethyl hexane could have the methyl groups on the same side of the carbon chain or on the opposite side. Does this make a difference, and would we identify them as cis/trans?

->Struggling Topic 3: Is there a difference between carbon tetrabromide and tetrabromomethane? It seems to me like they are the same CBr4.

__11.4: Properties of Alkanes__ -> Summary: Alkane boiling points are determined by the number of carbon atoms in the alkane and the alkane's structure. Smaller alkanes have lower boiling points, and larger alkanes have higher boiling points. Generally speaking, cycloalkanes have higher boiling points than continuous alkanes, and continous alkanes have higher boiling points than branched alkanes. Combustion reactions include hydrocarbons, like alkanes, and oxygen in the reactants with carbon dioxide and water as products. Carbon atoms are classified as primary, secondary, or tertiary depending upon how many other carbon atoms the atom is bonded to. Primary carbon atoms are bonded to only one other carbon atom, secondary carbon atoms are bonded to two other carbon atoms, and tertiary carbon atoms are bonded to three other carbon atoms. Finally, halogenation is the reaction of an alkane with a halogen to form a haloalkane.

->Struggling Topic 1: Which factor affects boiling point to a greater extent, the shape of the compound or the size of the compound? In general, it seemed like the size of the compound had a larger impact on the boiling point, but I didn't view sufficient examples to be sure.

->Struggling Topic 2: Is there any application for quaternary carbon atoms, carbon atoms that are bonded to four other carbon atoms? I suppose we could write a butane compound like 2,2-dimethyl butane that would have a carbon bonded to four other carbons.

__11.5: Functional Groups__ -> Summary: Alkenes, Alkynes, aromatic compounds, alcohols, ethers, aldehydes, carboxylic acids and esters are all functional groups. These groups affect the properties of the compounds in which they are found. Alkenes have a double bonded carbon atom, alkynes have a triple bonded carbon atom, aromatic compounds have six carbon atoms in a ring with six hydrogen atoms bonded around them, alcohols have a hydroxyl group bonded to a carbon atom, ethers have an oxygen atom bonded to two carbon atoms, aldehydes have a carbon atom double bonded to an oxygen atom and single bonded to a hydrogen atom, carboxylic acids have a carbon atom double bonded to an oxygen atom and single bonded to a hydroxyl group, and esters have a carbon atom double bonded to an oxygen atom and single bonded to another oxygen atom.

-> Struggling Topic 1: Is there a pronunciation difference between alkene and alkyne? If there is not a difference in pronouncing these, then how do you verbally communicate when an alkane has a double bond or when an alkane has a triple bond?

-> Struggling Topic 2: Is an amide group always present on the end of a carbon chain, or could the chain continue after the C(O)NH? I don't think I've seen any examples of this, but I wanted to double check.

__12.1: Alkenes and Alkynes__ -> Summary: Unsaturated hydrocarbons, alkenes and alkynes, have fewer hydrogen atoms than alkanes. Naming alkenes and alkynes is very similar to naming alkanes, but the longest carbon chain (that generates the base name) must include the double/triple bond, you always start numbering from the end of the chain closest to the double/triple bond, and the number of the carbon that has the double/triple bond on it is given before the alkene or alkyne base name (Ex: 2-pentene).

->Struggling Topic 1: How would you name an alkene that has two double bonds? Would you number them both like 2,4-dipentene? How would this work for cycloalkenes? Would you number only the second double bond for cycloslkenes and give it a prefix, like 3-dicyclopentene? This would assume that there is a double bond between carbon atoms 1 and 2, and then the 3 in the name would tell us that there is another double bond between carbon atoms 3 and 4.

->Struggling Topic 2: If the same compound has a double bonded carbon pair and a triple bonded carbon pair, is it named like an alkene or an alkyne? How would you name a molecule like this? Let's say that hexane had a double bond between carbon atoms 2 and 3 and a triple bond between carbon atoms 4 and 5. Would a compound like this exist, and how would we name it?

__12.2: Cis-Trans Isomers__ -> Summary: Isomers in alkenes can be Cis or Trans because the group connected to the double bond remains on the same side of the double bond. Cis isomers have groups on the same side of the double bond while trans isomers have groups on the opposite sides of the double bond., when cis-trans isomers don't exist, naming cis-trans isomers

-> Struggling Topic 1: I don't think cis and trans isomers exist in aklynes because the bond angle of a carbon triple bond is always 180 degrees. Is this correct? This makes me think that an alkyne would behave more like an alkane than an alkene since its structure could still be linear and unbent.

-> Struggling Topic 2: Are there alkenes with more than one double bond? If there are, would it be possible for part of the compound to be cis and the other part to be trans? Let's say that we have an octene with double bonds between carbon atoms 2 and 3 and 6 and 7. Could the 2-3 side be cis while the 6-7 side is trans? If it is, how would we name this? Would it be cis-2-trans-6-dioctene?

__12.5: Aromatic Compounds__ -> Summary: Aromatic compounds have a benzene ring which is composed of 6 carbon atoms bonded in a ring where each carbon atom has a single hydrogen atom bonded to it on the outside of the ring (the 4th bond for each carbon atom is "shared" between the others). If a benzene ring is a substituent, then it is named like other substituents with the name phenyl. If the benzene ring is the main part of the compound, then substituents around it can be named in several ways. If there are two substituents, the prefix ortho (o), meta (m), or para (p) indicates a 1-2, 1-3, or 1-4 arrangement respectively. When there are more than 2 substituents, the numbers are used to show their arrangements so that the lowest numbers may be used. Then the substituents are listed in alphabetical order.

-> Struggling Topic 1: Is it because benzene rings are symmetrical that any combination of 2 substituent aromatic compound may be covered using only m,o, or p groupings? There isn't a cis-trans difference between the "left" and "right" side of a benzene ring, is there?

-> Struggling Topic 2: How do you determine when a benzene is a substituent and when it is the main part of the compound? For example, ibuprofen has the benzene ring in between a three carbon atom chain on one side and a two carbon atom chain on the other side: CH3CH(CH3)CH2-benzene-CH(CH3)COOH. Would this be a variation on a p-ethyl propyl benzene, or how would we go about naming this using the IUPAC naming system?

__12.6: Properties of Aromatic Compounds__ -> Summary: Aromatic compounds have higher melting points and boiling points than other organic compounds. All are less dense than water, and only some with alcohol or carboxylic acid groups are soluble in water. The p isomer has a higher melting point and boiling point than the m and o isomers. The most common reactions with aromatic compounds are substitution reactions. This is where a hydrogen atom on the outside of the benzene ring is replaced by another atom or group of atoms such as a halogen, a nitrate group, or a sulfate group.

-> Struggling Topic 1: What causes the halogenation of methylbenzene (toluene) to produce very little meta isomers? I would have guessed that it would have produced fewer ortho isomers based on its closer proximity to the methyl group. Is there a dispersion forces explanation for this?

-> Struggling Topic 2: Is a substitution reaction classified as a form of replacement reaction? It seems to me like the halogen atom takes the place of a hydrogen atom in halogenation and forms a new product. Would it be more correct to identify substitution as a type of replacement reaction or as its own category all together?

__Critiques of this chapter__ --A. How clearly the author communicated individual topics --->11.5 - the table of functional groups on p.434 helps me quickly compare the many functional groups we covered. Without a quick reference table like this, I would have had trouble becoming familiar with these groups. --->12.1 - the way the author broke the naming of compounds down to simple steps was very useful - ex: p.447 and naming alkenes and alkynes.

--B. Specifics about the amount of content (did you need more examples?) --->12.1 - I would have liked to see some examples of compounds with more than one double or triple bond (if these exist). If these don't exist, I would like to have read about that here. --->12.6 - I would like to have seen more examples of different kinds of aromatic compounds and boiling points of the compounds to help me understand the relative differences in the compounds and the way these affect the compounds' boiling points (and other properties).

--C. Chapter's place in the overall text --->11.4 - Introducing combustion reactions of hydrocarbons is correctly placed after we have balanced many equations because these are usually difficult equations to balance. Also, it is good that we have covered replacement, synthesis, and decomposition reactions previously. --->12.6 - Introducing substitution reactions with benzene rings is rightly placed after we have covered replacement, synthesis, and decomposition reactions.