Chemistry: molecular weight of fats and oils

Tutoring organic chemistry, the composition of a fat or oil might be of interest. The tutor shares a resource.

Today, my reading sent me after the molecular mass of a typical fat or oil. I found the triglyceride molecular weight calculator (which I will call TMWC). It definitely answered some of my questions.

Fats and oils are collectively called lipids, but also triglycerides. The TMWC allows you to prescribe various parts of the fat or oil molecule (“build your own”), or else just select a typical one from a dropdown list. Then, it calculates the molecular mass of the fat or oil you’ve described.

I learned from the TMWC that soybean oil has an average molecular mass (some would say molecular weight) of 872.33. Its average molar mass would then be 872.33g. Beef tallow, interestingly enough, has a lower average MM: 850.92g.

I’ll be talking more about fats and oils in coming posts:)

Source:

triglyceride molecular weight calculator

biodiesel.org

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Organic chemistry: cis and trans

The tutor gives a simple explanation of why trans fat may be disadvantageous.

Cis and trans compounds have the same chemical formula but are shaped differently. With both cis and trans, a row of atoms experiences two irregularities.

The cis pattern navigates the two irregularities in such a way that it ends up on the same side whence it started. The letter “c” is a good way to think of “cis”: the letter starts and ends at the right.

The trans pattern ends up opposite whence it started. Letter “z” is a good illustration of the trans pattern: it starts at the left, but ends at the right.

I’ve heard that trans fat is to be avoided. (I’ve never heard that cis is better, just that trans is not preferred.) The reason, as I understand, is that trans fat molecules, because of their zigzag geometry, stack alongside each other more easily than do cis fat molecules. Since the trans fat molecules stack together more easily, they can be more difficult to separate as well. Therefore, they have a stronger potential to form layers inside blood vessels.

Cis and trans are examples of isomerism. Isomers are molecules with the same formula but different arrangment of the atoms. Organic chemistry has so much focus on isomerism, I could easily write twenty posts about it. I may, in time….

HTH:)

Source:

Solomons, T.W. Graham. Organic Chemistry, 4th ed. Toronto: John Wiley &Sons, 1988.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Organic Chemistry: sn1 reaction

The tutor describes  a fundamental reaction of organic chemistry.

In yesterday’s post I explained the concept of solvation. While that post discussed solvation in the context of dissolving salts, solvation can also happen with organic species. In particular, you could suggest that solvation facilitates the organic sn1 reaction.

Sn1 refers to a substitution reaction in which the reactant has a target group that is eventually removed by attraction to the solvent. The target group is also referred to as the leaving group:

Once the leaving group is pulled away, a vacancy is left:

The vacancy is immediately filled by a replacement group, which can be a solvent molecule or some other species mixed with the solvent:

A condensed description of the sn1 reaction is that a replacement group is substituted in place of the leaving group.

With sn1, the rate determining step is the first one; ie, the removal of the leaving group.

I’ll be talking more about organic chemistry reactions in coming posts. HTH:)

Sources:

IUPAC Gold Book

Solomons, T.W. Graham. Organic Chemistry, 4th Ed. Toronto: John Wiley & Sons, 1988.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: monomers and polymers

Tutoring Biology 12, you cover this concept.  The tutor approaches it from a simple, practical point of view.

You normally hear about monomers and polymers in organic chemistry.  Think of the name polyester:  it’s a polymer of esters.  The esters, then, are the monomers.

A commonly used analogy is a necklace of beads.  The entire necklace, altogether, is the polymer.  The beads are the monomers.  They don’t have to be the same as each other, but are similar.

So, a polymer is a molecule consisting of many monomers bonded together. The monomers found in a polymer are of the same chemical family, if they’re not the same.

Let’s accept the idea that the biological molecules fall into four basic categories: carbohydrates, lipids (aka fats and oils), proteins, and nucleic acids.  Three of these can easily be imagined as polymers, with their monomers shown below:

Polymer Monomer
carbohydrate (incl. starch, sugar, or glycogen) simple sugar, aka, monosaccharide; eg, glucose
nucleic acid (DNA, RNA) nucleotide
protein amino acid

So, you might say that “protein is to amino acid as carbohydrate is to monosaccharide.” Or, “DNA is to nucleotide as necklace is to bead.” However you imagine it, familiarity with the concept – as well as the specific cases – is important for biology and organic chemistry students.

While lipids are made from smaller units, the units are not all from the same chemical family. Hence, lipids don’t easily fit the “polymer” idea the way that carbohydrates, proteins, or nucleic acids do. However, I’ll talk more about lipids in a future post.

Good luck to all my students in this weekend’s biology conference:)

Source:

Mader, Sylvia S. Inquiry into Life, 11th Ed. New York: McGraw-Hill, 2006.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Organic Chemistry: naming alcohols

At university, the tutor encountered the world of organic chemistry – as many of you have or will.  Although it comes up rarely in high school tutoring, a basis is beneficial before you face it at post-secondary level.

If you haven’t read my earlier organic chemistry articles here and here, you may wish to do so. Continuing from them, we look today at naming alcohols.

Example 1: Name this molecule.

Step 1: Count the carbons in the chain. In this case, we have 9.

Step 2: Refer to the table in this post, which gives the name of the chain based on its number of carbons.

Step 3: Counting from the end of the chain closest to the OH, decide which carbon the OH is on. In this case, OH is on the fourth carbon.

Step 4: The name starts with the number of the carbon that has the OH, followed by a hyphen, then the chain name from Step 1. At the end of the chain, replace -ane with -ol, which means the molecule is an alcohol.

In our example, the OH is on the fourth carbon. The chain has nine carbons, suggesting nonane. Therefore, our molecule is 4-nonanol.

OH means alcohol in the context of organic chemistry. Not all molecules with OH are alcohols; nevertheless, OH is called “the alcohol group”.

Here are a couple more alcohols:

A final example reminds the student to count from the end of the chain that is nearest the alcohol group:

Many people might mistake the alcohol above for 5-hexanol. However, since the OH is nearer the bottom, you count up from there.

There are many more complicated alcohols – and of course other organic molecules – to name. Look for them in future posts:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Organic Chemistry: Simplified drawings

When you tutor high school chemistry, you cover a little organic chemistry. Today we visit a topic that rarely gets asked about during tutoring, but is very useful to know at the college level.

 
In my previous post on organic chemistry, I introduced the topic and showed a few drawings. They were of this style:

Recall that carbon, which appears as C in the diagrams, makes four bonds. (Each bond is a line to another atom.) Notice that most of the bonds are between carbon and hydrogen (H).

Since bonds usually are between C and H, chemists often don’t draw the H atoms. They’re understood to be there unless a bond clearly goes to something else. In such cases, only the bonds between carbons or between carbons and other atoms are shown, like so:

With the hydrogens left out, the diagram becomes simpler to understand. For example, you can more easily tell the how many carbons it has.

Some people take simplification a step further, writing only sticks for the carbon skeleton. Each corner represents a carbon atom. Therefore, all three of the following diagrams show butane:

The simplified drawing styles really come in handy for showing molecules with features such as alcohol. Here’s an example:

How we know the molecule is 2-pentanol will be covered in a future post:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Organic chemistry: a beginning

The tutor knew that eventually, he would discuss organic chemistry.  While it might be mentioned only briefly in high school, it is important at university.

Organic chemistry is a bit different from the chemistry most students are first taught. Yet, in real life, organic chemistry is a much bigger field.  Plastics, drugs, insecticides – they’re all organic.

Here, we need to clarify a definition.  “Organic” now has two meanings.  The grocers and naturalists define it as “natural.”

To a chemist, however, “organic” means “carbon-based.”  Hence, from a chemist’s point of view, DDT is organic.

Recently the two definitions came into direct conflict when one of my students said her water was “organic.”  What she meant, of course, was that the water was “from a natural source.”  From a chemistry point of view, though, you can’t have organic water.  Being H2O, water is not carbon based.

Organic chemistry is a huge topic. In the beginning, nomenclature (how to name the compounds) is the focus. We’ll start today with some of that.

An alkane is an organic compound with only single bonds between the carbons. If it’s an alkane, but nothing more besides, then it just contains carbons and hydrogens. An example is propane:

This compound is propane because it has three carbons. Each joining line is a bond. Carbon makes four bonds and hydrogen makes only one, which dictates the structure of an alkane once you know how many carbons it has. You can tell an alkane because it ends in “ane”.

As the number of carbons grows, different arrangements become possible. For example, here are two possibilites for pentane:

Both structues are pentane since both have five carbons. Alkanes are named by how many carbons they contain as follows:

number of carbons name of alkane
1 methane
2 ethane
3 propane
4 butane
5 pentane
6 hexane
7 heptane
8 octane
9 nonane
10 decane

There is much more to say about organic chemistry, even at the high school level. For further discussion, see future posts:)

Source: Solomons, T.W. Graham. Organic Chemistry, 4th edition. 1988: John Wiley & Sons, Inc.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.