Photo
May 15, 2012
30 notes
The FDA recently chose not to impose new regulations on bisphenol-A, which has sometimes been used in food packaging. Let’s look at what bisphenol-A is, how it’s used to make materials, and why it can be harmful if people ingest it. Bisphenol-A is shown above. Like many chemicals, its name can tell you how it looks:  Bis (two) phenol (the red circle on the left: a benzene ring attached to an OH) A (acetone, where the 3 carbons in the middle come from) So bisphenol-A is made by reacting 2 parts phenol with one part acetone. These are all common chemicals that don’t cost a lot, so bisphenol-A isn’t too expensive to make. What makes it useful is the OH on each side. This makes it like a building block that can attach to something on each side. In other words, it can do something in two places or is bi-functional.  Building blocks that can attach on both sides can be used to make long chains. And polycarbonate (sometimes called Lexan) is a long molecular chain mostly made of bisphenol-A. Many things, like jet canopies, are made of polycarbonate. Unfortunately it’s also been used in food containers. We’ll talk about that next.

The FDA recently chose not to impose new regulations on bisphenol-A, which has sometimes been used in food packaging. Let’s look at what bisphenol-A is, how it’s used to make materials, and why it can be harmful if people ingest it. Bisphenol-A is shown above. Like many chemicals, its name can tell you how it looks: 

  • Bis (two)
  • phenol (the red circle on the left: a benzene ring attached to an OH)
  • A (acetone, where the 3 carbons in the middle come from)

So bisphenol-A is made by reacting 2 parts phenol with one part acetone. These are all common chemicals that don’t cost a lot, so bisphenol-A isn’t too expensive to make.

What makes it useful is the OH on each side. This makes it like a building block that can attach to something on each side. In other words, it can do something in two places or is bi-functional. 

Building blocks that can attach on both sides can be used to make long chains. And polycarbonate (sometimes called Lexan) is a long molecular chain mostly made of bisphenol-A. Many things, like jet canopies, are made of polycarbonate. Unfortunately it’s also been used in food containers. We’ll talk about that next.

Tags: science chemistry bisphenol-A polymers polymer science molecules

Photo
August 23, 2010
38 notes
Carbon likes to have four bonds to other elements. You can see from the periodic table that it is four spaces from both the left and right ends of the table. For this reason, it wants to share 4 electrons. In organic chemistry you draw a lot of structures that show the compositions of molecules. The letters represent atoms, and the lines represent bonds between atoms, holding them together. These are called covalent bonds, and each line is the sharing of 2 electrons. Methane, the structure at the top, is the main component in natural gas, and is the simplest organic compound: CH4. Its shape is a tetrahedron, and the fat and dotted bonds simply show that those hydrogens are going into and coming out of the screen. Ethanol is an “alcohol” and is the active component in alcoholic drinks. People have also experimented with using ethanol instead of gasoline as a fuel for cars. Formaldehyde is an important precursor for many industrial chemicals. You can see it has a double bond, which means the C and O are sharing 4 electrons instead of 2.

Carbon likes to have four bonds to other elements. You can see from the periodic table that it is four spaces from both the left and right ends of the table. For this reason, it wants to share 4 electrons. In organic chemistry you draw a lot of structures that show the compositions of molecules. The letters represent atoms, and the lines represent bonds between atoms, holding them together. These are called covalent bonds, and each line is the sharing of 2 electrons.

Methane, the structure at the top, is the main component in natural gas, and is the simplest organic compound: CH4. Its shape is a tetrahedron, and the fat and dotted bonds simply show that those hydrogens are going into and coming out of the screen.

Ethanol is an “alcohol” and is the active component in alcoholic drinks. People have also experimented with using ethanol instead of gasoline as a fuel for cars. Formaldehyde is an important precursor for many industrial chemicals. You can see it has a double bond, which means the C and O are sharing 4 electrons instead of 2.

Tags: chemistry molecules organic chemistry structures science