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I am writing a dystopian future where I hope to make it possible that specific emotions can be taken in the form of pills or drug form; or, combined pills taken to form more complex feelings. Obviously there are certain chemicals associated with emotions such as serotonin and endorphins. But are there specific chemicals that could be used to create something very close to taking a drug and it giving you an overwhelming sense of sadness, jealousy or rage?

Are there hormones and chemicals specific enough for this, or would it have to be combined with some kind of visual aid to create context to then be able to feel sadness more, for instance? (Although this kid of defeats the point, as in my world these drug forms of emotion are meant to be taken by those incapable of creating it naturally themselves).

This is a big area of research at the moment. (I'll add some pointers to research as and when I'm online)

The answer is almost certainly yes but there is a long way to go. However it will rely on drugs that can be accurately targeted.

EDIT - to clarify
If you could isolate the chemicals in a human brain and inject those same chemicals into the brain of another person, but precisely into the same brain structures then I assert that the second person would experience the same emotions. Once we know what all these chemicals are and where to send them then with sufficient (very advanced) technology, we could replicate the same.
We couldn't replicate the other person's thoughts - just the emotions.
This might require nano-machines (also currently being worked on) to make sure the drugs were accurately delivered.

At present if someone takes an antidepressant or an amphetamine it floods the whole system and not just the brain (there may be some preferential uptake). There are centres in the brain (still not fully understood) which when stimulated by an electrode can cause changes in emotion.

It's complicated because a drug that causes excitation in one sort of synapse in one organ can suppress it in another.

Once the technology to precisely target small brain centres is achieved then your scenario is possible.

Notes

You didn't give a hard-science tag (thank goodness!) so I am relying on remembered facts from studies some time ago.

If someone paid me I could probably back my answer up with the relevant research but it would perhaps take hours. Maybe I'll find some pointers that I can add on here for you to read up on.

Provisos

1. Some emotions can be very close to each other in physiological terms - for example mild fear and excitement (both involve adrenaline). It may be necessary for the subject to prepare mentally or hypnotically to avoid a 'bad trip'. However there are different brain structures that could be stimulated in addition to merely giving adrenaline. The combination could distinguish between fear and excitement. So a complex targeted drug could work.




2. Pleasant emotions could be very addictive.




3. The pills may have undesirable long-term effects.




4. Added To get perfect results it might be necessary to tailor the proportions of drugs to each individual to get the right balance. This could be achieved by a DNA analysis together with a brief personality test.

List of references (in progress) Note that typing these terms into YouTube will usually give a layperson's guide.

Cognitive and emotional influences in anterior cingulate cortex http://www.georgebushmd.com/GBMD-Website/Research_&_Publications_files/Bush_2000_TICS_CingReview.pdf

Vagal tone and the physiological regulation of emotion. [This refers to the Vagus Nerve] https://www.ncbi.nlm.nih.gov/pubmed/7984159

How the Brain Processes Emotions

When it comes to emotions, it turns out that there are regions in the
brain, specifically in the limbic system, that are associated with
each of the 6 main emotions. Emotions are actually experiences that
are associated with activation of certain regions in the brain.
http://www.neurologytimes.com/blog/how-brain-processes-emotions

The gut-brain connection https://www.health.harvard.edu/diseases-and-conditions/the-gut-brain-connection

Chemosignals Communicate Human Emotions
https://journals.sagepub.com/doi/abs/10.1177/0956797612445317

Biochemical Variables in the Study of Temperament https://link.springer.com/chapter/10.1007/978-1-4899-0643-4_10

Some psychiatric medication is used to change the affect of patients: anti-depressants diminish sadness, depressants diminish joy, anxyolitics reduce fear, anxiogenics increase fear, there are drugs that make aggressive and drugs that reduce aggression, and so on.

The problem with all of this is that every human brain is different, and that not everyone reacts to the same drug in the same way. Which is why there are so many different anti-depressants, for example, and why for some patients none of them work (or not in the expected way or not without adverse effects).

So while it is easily possible to create a drug that will induce a specific emotion in a single individual (given enough time to research that individual), it is impossible to create a drug that will have the same effect on everyone.

Not really, since there's a mental component to feelings. Basically, you need something to be sad*, jealous, or mad about to get the full emotional effects. If you've ever had allergy testing, you might actually have experienced something like this. When the tests are finished, the doctor gives you a shot of adrenaline https://en.wikipedia.org/wiki/Adrenaline to counteract any lingering effects. This of course is the same hormone evoked in "fight or flight" situations, so you experience the physical component of the emotional response, without there being anything to fight or run away from.

*Though see depression and the use of antidepressants.

I think there might be a way.

As other answers have mentioned, emotional responses are pretty complicated things.

Some emotions are more readily induced or modulated than others, and the more complex the emotion the more complex the means of effecting it needs to be.

Some real-world foods can make you happier some of the time simply because they're high in carbs. High-carb foods reduce stress hormone release in the brain.

As has been mentioned already, getting very precise at this point seems to require access to the inside of the brain itself and being able to distinguish between and selectively modify specific regions in specific ways.

The solution depends on how techy you want your story to be. If you're both going for a super high tech/robotic setting and want accuracy, you could use nanobots that migrate to specific regions of the brain on their own over time, then receive signals of some form or other in order to provide the necessary response.

ie:

acquire nanobots

nanobots migrate to their specified locations

nanobots recieve signal

appropriate nanobots release/trigger release of appropriate neurotransmitters

This signal could come in various forms and could even be food if you figured out how to send specific messages to the various nanobots based on food consumed.

Maybe you could just find some set of neutral compounds that don't exist in food/other ingestables and have a different set of nanobots in the digestive tract that detect the presence of those and their relative proportions, interpret those proportions as a specific emotional response, then send the correct message to the nanobots in the brain.

Some kind of wireless mesh network between the nanobots might be able to simplify this whole system enormously, but I'm not sure how capable those wireless systems would actually be. Range in particular would be an issue between the stomach/intestines and the brain. This might be solvable with some kind of relay network across that distance.