The Science Behind Household Cleaners
One of the things I love about science is that it is behind most things we do and encounter in our daily life. Even when you put aside all of the science going on in our bodies you don’t have to go far to see science in action. Take something in our everyday life, an often mundane task, household cleaning. It’s really all about chemical reactions. Our everyday cleaners have their basis in science. The ingredients allow for our clothes to be clean, our kitchen countertops to be free of any food-borne germs, and our bathrooms to be sanitary. If one takes the time to look into these cleaners they each provide a science lesson.
The first household cleaner that comes to mind is bleach. We use it to keep our whites white in terms of our laundry but it is also used around the house in other ways. Most people use it to clean their bathrooms and it can be used to disinfect children’s toys among other things. Investigating what exactly bleach is, I figured I’d come up with the chemical formula behind the common name. The first cleaner I took a look at was my multi-purpose Clorox wipes and lo and behold, they are bleach-free. This was a surprise since I, like many other people, associate the brand name Clorox with bleach. My Clorox cleaning wipes don’t actually contain bleach, what do they contain? The active ingredients are two ammonium chlorides, one an N-Alkyl Dimethyl Ethylbenzyl Ammonium Chloride and the other an N-alkyl Dimethyl Benzyl Ammonium Chloride. For both the N-alkyl refers to a carbon chain of varying lengths, denoting by the ‘N.’ Each ingredient contains a mixture of these varying carbon chains, the label specifies the chain length and percentage in the mixture. For example the first has a mix of C12 (68%) and C14 (32%). Each of these components is present at only 0.145% of the entire solution but represent the active components of the wipes.
Both of the compounds listed above are classified as Quaternary Ammonium compounds, where the four hydrogen groups of ammonium, NH4+, are replaced by organic groups. In the case of the two found in Clorox wipes, one of the groups replacing a hydrogen is the long carbon-chain alkyl and these chains are known for their disinfecting properties, effective against microbes and bacteria. Benzalkonium chloride, another name for N-alkyl Dimethyl Benzyl Ammonium Chloride, is a surfactant and disinfectant. It is thought to have its effect on various micro-organisms by upsetting the cell membrane, the lipid bilayer, and thus disturbing intramolecular interactions. The cell membrane controls traffic in and out of cells and attacking it can negatively affect the overall well-being of the entire cell and in the case of small micro-organism the entire organism.
So based on this new knowledge of my Clorox wipes being ‘bleach-free’ I then took a look at my Clorox Clean-up which I use on my toilet bowls. The label says it does contain bleach, now we are getting somewhere. Listed as the active ingredient is sodium hypochlorite at 1.84%, About.com elaborates that chlorine bleach contains this as its active ingredient. Here’s the relationship I was seeking, bleach is the common name and sodium hypochlorite is the chemical name. But it’s not quite that simple- About.com goes on to distinguish between chlorine bleach and oxygen bleach. Oxygen bleach contains either hydrogen peroxide or a peroxide releasing agent. And another distinction is needed between oxidizing and reducing bleaches depending on their mode of action. In all cases bleach works to disrupt the color reflecting properties of chromophores. Chromophores, as the name implies, are a class of compounds that absorb light at specific wavelengths and thus appear to be a given color. Bleach works to either break or alter bonds to mess with chromophores’ optical properties depending on the type (oxidizing or reducing). This was news to me, there isn’t one chemical compound behind all bleach, instead bleach is a term for any chemical that cleans and disinfects often by removing color from its target.
Sodium hypochlorite (NaOCl) is an example of an oxidizing bleach. Sodium hypochlorite can be made by mixing chlorine gas with NaOH, sodium hydroxide, to get NaOCl (this process also yields NaCl).
Cl2 + 2 NaOH → NaCl + NaClO + H2O
Chlorine in general terms is a disinfectant, a stain remover, and it kills bacteria and algae. When chlorine and water are put together the products are hypochlorous acid (HOCl), hydrochloric acid (HCl), and oxygen. The oxygen reacts with chromophores to disrupt their optical properties. Clorox.com lists sodium hypochlorite as the active ingredient of bleach that whitens, brightens, and removes dirt and stains from surfaces and fabric; as well it is effective in killing 99.9% of bacteria, viruses, and some types of mold. How does bleach do all of these? Well we have already touched upon the method by which bleach whitens and brightens. But what about chlorine bleach’s other properties-the bacteria, virus, and mold killing?
Chlorine’s germ fighting abilities were first noted in the late 1800s by none other than Louis Pasteur, the same scientific big-wig responsibility for some of the first vaccines, the process of pasteurization, and other key contributions to the field of microbiology. In 2008, researchers pinned down the exact link between sodium hypochlorite and micro-organisms. Ursula Jakob et al. at the University of Michigan showed in Cell (Nov. 2008) that hypochlorous acid, one of the breakdown products of sodium hypochlorite when it comes in contact with water, unfolds and irreversibly aggregates essential bacterial proteins rendering the bacteria itself inert. In the vast gap between these two time points, studies have been done investigating sodium hypochlorite mechanisms but for the most part have served only to rule out not establish the exact mode of action. The working hypothesis was the chlorine, once it is introduced as the cleaning agent, in its various forms disrupts micro-organisms by getting in through their cell membranes and interacting with essential factors. The task of specifically linking chemicals found in cleaning products to their exact mechanism of action proved to be a little tougher than I expected while researching this topic. On the other hand there is a general attitude in science that if something is proven to work, in the case of bleach killing micro-organisms, its credibility remains even if the specifics aren’t clear.
As my research on this topic continued, I found a website The Laundry Alternative Inc which spells out the types of oxygen bleach available. We’ve all seen the infomercials advertising Oxiclean, the major oxygen bleach and alternative to chlorine bleaches. I never realized there was a tug of war between the two, but a quick search online shows a myriad of sources comparing them side by side. It seems for a long time people were content with only one option- chlorine bleach. But now there is another option out there- oxygen bleaches.
So the next time you are trudging through a load of laundry or cleaning your bathrooms, just think of all the mystery and drama surrounding your cleaning agents. Have scientists even come up with what exactly makes your particular cleaning agent work? Or are the details still under investigation? And which side of the bleach debate are you on- chlorine or oxygen? Unsure- you could always conduct your own scientific experiment comparing the two bleaches side by side. See science can make routine household chores interesting.
Sources available upon request