How To Make Cakwe

The one that I missed during Ramadhan is Cakwe. Almost every breaking fasting time, I eat Cakwe at home. I love Cakwe very much. But, in Japan, I couldn't find it but I didn't give up, so I tried to make it by myself. After googling, seeing cookpad, and youtube, here is my recipe: 

Ingredient:

1. Wheat flour

2. Baking powder

3. Yeast

4. Garlic powder

5. Salt

6. Water

7. Vegetable oil

Procedure:

1. Put the wheat flour in the bowl.

2. Add baking powder and yeast around 1/10 of the wheat flour used. Add the garlic and salt as you want.

3. Add a little amount of water (do not too much), then mix it well

4. Add a little amount of vegetable oil too, then mix it

5. Prepare another bowl, cover the surface with the vegetable oil

6. Put the dough and add more oil and spread it along the dough

7. Cover it with plastic

8. Keep it in the fridge overnight

9. Check the texture, if still sticky, you can add more wheat flour

10. Next, it's time to make the shape. Prepare the cutting board by spreading the wheat flour on its surface in order to make it less sticky

11. Put the dough like the picture below

12. Cut the dough like the shape below

13. Put one piece on to another piece

14. Use the chopstick to make a splitting

15. Heat the vegetable oil, wait until hot, then fry the dough. Do not forget to pull the dough so it will stretch like the shape of Cakwe.

16. It's easy right, now you can have it with sambal kacang or mayonnaise. If you want to know how to make sambal kacang, I will tell you in a different post. 

What is SN1 and SN2 Reaction?

I found this analogy of cat and comfy chair from this website. It's really helpful in making me understand the concept of SN1 and SN2 reaction.

SN1 reaction happens just like the cat in the first row. The yellow cat wants to sit in the comfy chair, but it needs to wait until the grey cat leaves the comfy chair. So, once it's empty, the yellow cat occupies the comfy chair. So, the SN1 reaction is the substitution where the nucleophilic (the yellow cat) is not too strong so it can not get rid of the leaving group easily, it requires to wait until the leaving group leaves and the carbocation formed. This reaction is also called as unimolecular because the reaction is only depending on one thing that is the substrate only where the carbocation formed. The tertiary alkyl halide, for example, is the most possible/the fastest than the secondary and primary one. Because the tertiary one is having the most stable carbocation. Mostly the product of the substitution is a racemic or the mixture of retention and inversion.

While the SN2 reaction occurs like the cat in the second row. The yellow cat is strong enough to get rid of the grey cat, so the grey cat is forced to leave the comfy chair. So, the SN2 reaction is the substitution where the nucleophilic is strong enough so it can get rid of the leaving group easily. This reaction is depending on two things: the substrate and the nucleophilic, so that's why this reaction is bimolecular. It depends on the type of the substrate, the primary one is easier than the secondary and tertiary. Because in tertiary one, the steric hindrance is big enough to hinder the nucleophilic to get rid of the leaving group, while it's so easy with the primary one where is no steric hindrance. As just mentioned earlier, not only the substrates, the nucleophilic itself is also affecting the SN2 reaction. The more concentrated the nucleophilic it is, the faster the reaction goes. 

What is %ee? Chiral HPLC?

What is %ee? ee is the abbreviation of enantiomeric excess, a measurement of purity of chiral substances. As an example, there is a sample that contains enantiomers: X and Y. The optical rotation for X is 60 degrees. However, when X exists with Y, the optical rotation becomes 30 degrees. So, how much is the %ee? From this case, we also can conclude that X is available in a higher amount than Y because X that rotates while Y is turned off. If the X optical rotation becomes 30 degrees, means that the remaining 30 degrees were canceled by Y optical rotation. Then to calculate the %ee of X, let's see the formula below: 

The calculation above for determining the %ee is obtained from optical rotation measurement. Besides that, %ee can be also calculated from the measurement using chiral HPLC. We just need to compare the area of the enantiomers. For example:

When using HPLC, if we use column with conventional reversed phase, we only can separate the diastereomers. If we want to separate enantiomers, we require chiral stationary phase. To know the difference between diastereomers and enantiomers, see this post. 

How can Chiral HPLC separate enantiomers? The HPLC uses a single-enantiomer stationary phase. Therefore, the separation depends on the affinity of the analyte to the single-enantiomer stationary phase. So, the enantiomers will exit the column at different time.  

The chiral stationary phase usually be prepared by attaching the chiral compound to the surface of achiral compound such as silica gel. 

An example of chiral column is CHIRALPAK and CHIRAL CEL, these are a well known chiral chromatography column produced by Daicel. Daicel had been developing these products since 1980s.