Sunday, June 3, 2018

A Brief Note: Stereoisomers

Natural products are various in chirality and rich in enantiomer. Enantiomers is one of the isomers types. Isomer is the term for a molecule which has different features because of different molecule structure arrangement even though the number of the atoms is the same. There are so many types of isomers. 

Structural isomers mean a compound with the same formula can have various forms of its structure. This type of isomers includes chain isomerism, position isomerism, and functional group isomerism. While in the stereoisomers, the bond structure is the same, but the position of the atom in spatial is different. This group includes diastereoisomers and enantiomers. What makes diastereoisomers and enantiomers different are, diastereoisomers are the conformational isomers which are not mirror images of one another and are not superimposable, while enantiomers are mirror images of one another and are not superimposable. To make it clear, see the picture below.

Vibrational Circular Dichroism (VCD) Spectroscopy is a spectroscopy that can assign stereoisomers because it can differentiate the absorption of left and right circularly polarized light. Here, we have 2 important keywords, Left Circularly Polarized (LCP) and Right Circularly Polarized (RCP) Light. The unpolarized light can not differentiate stereoisomers, the result of the measurement using samples which contain two enantiomers is identical, so it fails to differentiate it. Circular dichroism appeared as the solution to assign two enantiomers, because the light used is the polarized one. The polarized light wave comes through an optical device and then converts the light into a circularly polarized light: RCP and LCP.

If the sample is the chiral compound, then the spectrum will be different, but no for achiral compound, the spectrum will be identical. Therefore, the principal of this assignment is using CD spectrum. There are so many kinds of instrumentation for the measurement, one that was quite popular was Electronic CD (ECD) spectroscopy. The instrument was always developing, then we know VCD Spectroscopy, which the circular dichroism occurs due to vibrational excitations.

That's all. If there is any mistakes, I beg your pardon. You may help me revise it if you know what is more correct. Anyway, thanks for visiting :)

Saturday, May 26, 2018

How To Make Bakwan

This month is the holy month for every Moslems in the world. Ramadhan comes, Ramadhan is the time when every Moslems is fasting in a month to feel the feeling how poor people face their life without food so we can be more generous to each other. Anyway, this month, I am not in my home country, I study overseas so I live without my family. We do fasting between the sunrise and the sunset, so after the sunset, we can break the fasting. Usually, I break the fasting together with my family. We sometimes have our favorite snacks which are any kind of snacks made by frying. One of them is Bakwan. I miss eating fried snacks, especially Bakwan in this case, with my family, to erase my homesick, I made my own Bakwan. 

Here are the ingredients:

1) Pepper (the amount depends on your taste, the more you add, the spicier it will be)

2) Red Chilies (the amount depends on your taste, the more you add, the spicier it will be)

3) Shallots

4) Salt (please, set adjust with your taste)

5) Sugar (please, set adjust with your taste)

6) Egg

7) Garlic (I used the mashed garlic), fresh garlic and then you mash it is also okay

8) Leeks 

9) Wheat flour

10) Vegetables (it depends on your taste, you can put bean sprouts or other things that you think is suitable, in my case, I only use cabbage)

11) Chilies powder

12) Flavoring

13) Coconut Oil

1) Mash the pepper

2) Cut the red chilies and shallots into pieces

3) In a bowl, put the wheat flour, add the eggs, mashed garlic, the pieces of leeks and shallots, salt, and sugar

4) Mix them well, you can add some flavorings and/or chilies powder, it depends on your preference.

5) Put the vegetables, mix them well. 

6) Prepare the hot coconut oil on the frying pan. Make sure that it is enough to deep fry the dough. 

7) Fry the dough

8) Finally, Bakwan is ready to be served

Wednesday, March 14, 2018

How To Make Rendang

In the next few months, Indonesian Moslems will celebrate the Eid Fitr. Usually, the main dish for the celebration besides Ketupat is Rendang. Here the ingredient that you need (the amount is as much as the picture below):

1. Red Chilies

2. Cumin

3. Candlenuts

4. Garlic

5. Shallots

6. Turmeric

7. Ginger

8. Galangal

9. Lemongrass Leaf

10. Coriander Seeds

11. Turmeric Leaf

12. Meat

13. Salt

14. Coconut Milk

15. Sugar

16. Coconut Oil

17. Water

1. Prepare the seasonings which consist of the red chilies, cumin, candlenuts, garlic, shallots, turmeric, ginger, coriander seeds, and salt. Grind and mix them well. 

2. Smash the galangal and lemongrass leaf.

3. Heat the coconut oil in the frying pan.

4. Put the seasonings no.1 and the smashed galangal, cook them well.

5. Add the coconut milk, mix them well. 

6. Put enough water, mix them well.

7. Add the meat.

8. Put the smashed lemongrass leaf and turmeric leaf. 

9. Cover the frying pan with its cover.

10. Wait until the meat cooked. During this process, you can add another salt, sugar, water, or coconut milk according to your taste. I spent more than 1 hour to make the meat cooked. 

11. Now, your Rendang is ready to be served.