Tag: Chemistry

Chemistry of Sunscreen

Stop by a Wallgreens or CVS and you’ll notice a large sunscreen selection, but each product has advantages and flaws. The differences, it turns out, depend on the chemistry of each active ingredient. If you’re in the United States, glancing at the list on the back of each bottle, you’ll see that products tend to have some combination of 8 common active ingredients.

But did you know that of the 8 most common active ingredients, there are actually only two different UV protection mechanisms? Categorized below, you’ll notice that UV filter compounds are much more common, while the mineral blocker type only include two of the main compounds.

Sunscreen lotion contains active ingredients that contribute to the sunscreen’s SPF, protecting you from sunburn by keeping UV rays from reaching your skin and damaging cells. Active ingredients protect you from UV rays in two unique ways:

Filtering:

This method filters or absorbs UV light, turning the radiation into heat energy, rather than allowing it to cause cell damage.

UV filters chemical ingredients: Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

  • Hazards of UV filters:
    • UV filters can and have been measured in blood of people who use sunscreen frequently. The main concern with these chemicals is endocrine disruption.
    • Oxybenzone is by far the most dangerous chemical found in sunscreen. It penetrates the skin easily and enters the blood stream. It has the ability to penetrate the blood-brain barrier, causing hormone disruption. It is estrogenically active and has potent anti-androgenic effects.

Blocking:

Blocks UV light from penetrating through the mineral ingredients in the sunscreen so that it never comes into contact with your skin. (ex. Zinc Oxide and Titanium Dioxide)

Pick up your tube of sunscreen and look at the back. You’ll see a number of active ingredients. Typically, you’ll see 4 or 5 Filtering type ingredients listed. The compounds that protect by Filtering will tend to absorb only certain wavelengths of light, so sunscreen companies include a combination of different ones to block a broader spectrum of UV rays.

Blocking type ingredients work in a different way, so they are present either by themselves or with a few filter ingredients. For example, you might have sunscreen that lists zinc oxide as the only active ingredient.

To avoid sunburn and more importantly skin damage from UV rays, elect for a broad-spectrum sunscreen with as high an SPF as possible, and ideally use a sunscreen that also contains Zinc Oxide or Titanium Dioxide.

UV blocking minerals: Zinc Oxide, Titanium dioxide

  • Hazards of mineral blockers:
    • Zinc Oxide and Titanium dioxide particles are photoactive, meaning they can create free radicals when exposed to UV radiation that damage surrounding cells. To mitigate this risk, manufacturers apply surface coatings to these particles.
    • Both of these mineral blockers are electrically charged molecules. Over time and due to heat exposure, these mineral blockers can settle or clump, leaving gaps in skin coverage. To be effective, mineral sunscreens contain ingredients that hold zinc oxide or titanium dioxide in a suspension to provide an even coating on the skin.
    • Titanium Dioxide creates more free radicals that do oxidative damage to your body and skin cells, and increases aging processes. Zinc oxide tends to have a broader-spectrum range of coverage than titanium dioxide, although the combination of both Zinc Oxide and Titanium Dioxide provide the broadest range of protection.
    • Zinc and titanium oxide may potentially harm environment.

Some products, such as “SheerZinc Face” by Neutrogena, will contain zinc oxide. Finding a product that contains both zinc oxide AND titanium dioxide is much less common due to the highly charged particles tendency to coagulate and cause clumping.

Conclusion:

As discussed, there are two different types of sunscreen. If you are going for a product that contains Mineral Blockers, Zinc Oxide is preferred over Titanium Dioxide. Check products that contain mineral blockers to ensure lotion consistency is homogenous and not de-coagulated because the clumps will cause gaps in skin coverage, thus causing you to get burnt.

Your ideal sunscreen might have the following active ingredients:

  • Homosalate (8–10%)
  • Ocinoxate (variable percentage)
  • Octocrylene (2–6%)
  • Zinc Oxide (5–15% +)

 

How To Get an A in Organic Chemistry

This post will describe the tool I used to review ALL of my organic chemistry notes in 1 hour. I will walk you through the steps and show you how I created and used the most fantastic study tools and aced o-chem.

My official college transcript displays Cs in general chemistry (101 and 102).  Below is a description of what I did to get A’s in organic chemistry. Unlike many liberal arts classes, orgo has no Achilles heel to give you an easy way out. No amount of last minute cramming will allow you to succeed.

If you’re like me, studying is more of a game than a task. The hard part about Orgo isn’t the actual material/concepts, but the large amount of information. Taking in all the information in orgo is like trying to drink water from a fire hydrant. Another challenge is siting down and actually studying when surrounded by friends in easier subjects who don’t need to study as much. If you’re the one carrying around that orgo textbook that’s a foot thick, use it as a reminder that you’re going to need to do something different than the kids taking poli sci.

Practice problems first. Choose to spend the majority of your study time on practice problems. Especially at the beginning of a new section/chapter. Work your professor’s assigned problems first. In my experience the most effective way to begin learning the material is by doing practice problems first rather than by making flash cards and trying to memorize reactions.

Getting Stuck. At times its going to feel like a new set of reactions can’t be distinguished from each other. You’re lost and you “don’t get it”. At this point, its time to switch from practice problems to a reading/memorization tactic. You may think of making flash cards but….

Make Flash Pages instead of flash cards. The point of a flash card is just that, a flash to spark your memory. Lets say you glance at 10 flash cards 1 time each. Each card takes between 5-10 seconds to look over. I believe that it is possible increase your glance surface area from the size of an index card to the size of an 8x11in sheet of paper. This will improve how much information you cover.
-In a glance of 5-10 seconds, your eyes view an entire page of condensed notes instead of a small index card.
-Your brain will be forced to recognize certain reactions and concepts right next to other reactions and concepts that are related.
To make them: copy the essential sections of a chapter section onto a blank page. Say you cover 6 chapters during a semester, with ~10 sections each. This means that if you make a flash page for every section, you will have made about 60 pages of notes. That’s less than a page per day.  When in the span of an entire semester, this is not much.

Look for the similarities. In many cases, the reactions are analogous to each other. For example: nucleophilic attack on a carbonyl carbon by a nucleophile is analogous to nucleophilic attach on a cyanide carbon by a nucleophile (you’ll know what this means later if you don’t now). Many of the mechanisms involve the same exact steps, which is great because it allows you to focus on a big picture. Understanding the general processes are key to then noticing the slight nuances between each specific mechanism, such as the differences between acidic vs. basic conditions.

Read Before Lecture. Just do it. Bite the bullet and spend some time (even 10 minutes) glancing at the material to be covered in the following lecture. If you are ambitious you can make your flash page on the section before class. This is useful for any class, but in reality is not normally actually done. If you want an A, do it for orgo. This will allow you to capitalize on the time you spend in lecture, and actually understand where your teacher is going during class.

You can try any memorization tricks you want, but as I said in another post, the goal with memorization is to maximize your Glances/Time ratio.

Do Not fall behind.

Supplemental material: I used “Organic Chemistry as a Second Language” by David Klein. There’s a version for both orgo 1 and 2. Utilize your textbook solutions manual. If your book doesn’t come with one, its definitely worth trying to find one on the internet – even purchasing used on amazon if you need to. Remember, work on practice problems first.

Check your syllabus and understand how the course will be graded. My professor’s policy was to drop each student’s lowest exam grade and not count it. So, I was able to accidentally blow one of the exams. Realize also that its easier to do well on homework assignments than it is on tests. So make sure you ace the homeworks and other general assignments so that you have a bit of a buffer when it comes to the exams.  If you have close to a B+ average on exams, this may average to an A/A- when combined with the high grades you receive on the general homework assignments. Play the game.

Lab Sections: Your class will probably have a required lab period. Lab was run by Teacher’s assistants. Go to T.A. office hours (one hour a week for me) and get help. Just ask a million questions and understand how they graded and you’ll be fine.

Get to know your professor. College professors can be phenomenal people. They’re incredibly specialized in their area, and you’ll learn more about the class speaking to them for an hour than spending two days studying alone.

Study Groups: Helpful for lab sections and writing lab reports, as well has comparing solutions to difficult practice problems and homework. Having a small network (maybe 2 to 5 people) that you can call on for help while studying will prove to be beneficial. I sincerely believe that I would not be graduating college this May with a chem major were it not for the group I studied with during some of my harder classes.

Go Out. Don’t spend every night studying, give your brain a break. Studies show that you can’t really focus on one thing for more than 45 minutes anyway. Spend part of every evening studying, sure. But keep in mind that those four years goes by fast, and there’s a chance you won’t ever use the information in organic chem again.

The next part is to Review, and maximize your Glances/Time ratio. The idea here is that its more effective to look over a page 5 times spending a 1 minute each time than it is to look over a page 1 time spending 5 minutes. Do this with the flash pages you make. Don’t worry if you have trouble reading so quickly. I’m one of the slowest readers you’ll meet. Force yourself to spend as little time as possible on each flash page when reviewing. You will improve your brains ability to interpret a large amount of material during a single glance. You will soon see how the sponge of your brain collects and retains more information by seeing it many times in short flashes.

This will shorten the time you spend studying for the class. Towards the end of the semester, the 60 flash pages that you made will become readable in 60 minutes or less if you use this technique. Isn’t that incredible? You now have a tool to get through an entire semester of organic chemistry in 1 hour.